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Abstract:

An inspecting apparatus for reducing a time loss associated with a work
for changing a detector is characterized by comprising a plurality of
detectors 11, 12 for receiving an electron beam emitted from a sample W
to capture image data representative of the sample W, and a switching
mechanism M for causing the electron beam to be incident on one of the
plurality of detectors 11, 12, where the plurality of detectors 11, 12
are disposed in the same chamber MC. The plurality of detectors 11, 12
can be an arbitrary combination of a detector comprising an electron
sensor for converting an electron beam into an electric signal with a
detector comprising an optical sensor for converting an electron beam
into light and converting the light into an electric signal. The
switching mechanism M may be a mechanical moving mechanism or an electron
beam deflector.

Claims:

1. An inspecting apparatus characterized by comprising:a plurality of
detectors each for receiving an electron beam emitted from a sample to
acquire image data representative of the sample; anda switching mechanism
for causing the electron beam to be incident on one of said plurality of
detectors,wherein said plurality of detectors are disposed within the
same vacuum chamber.

2. An inspecting apparatus according to claim 1, characterized in
that:said plurality of detectors comprise:a first detector comprising an
electron sensor for converting an electron beam into an electric signal;
anda second detector comprising an optical sensor for converting an
electron beam into light and converting the light into an electric
signal,wherein said electron sensor and said optical sensor are disposed
within said vacuum chamber.

3. An inspecting apparatus according to claim 2, characterized in that
said electron sensor of said first detector is an EB-CCD sensor having a
plurality of pixels, and said optical sensor of said second detector is a
TDI sensor having a plurality of pixels.

4. An inspecting apparatus according to claim 1, characterized in
that:said plurality of detectors comprise:a third detector comprising an
electron sensor for converting an electron beam into an electric signal;
anda fourth detector comprising a electron sensor for converting an
electron beam into an electric signal,wherein said electron sensors in
said third detector and said fourth detector are disposed within said
vacuum chamber.

5. An inspecting apparatus according to claim 4, characterized in that
said electron sensor of said third detector is an EB-CCD sensor having a
plurality of pixels, and said electron sensor of said fourth detector is
an EB-TDI sensor having a plurality of pixels.

6. An inspecting apparatus according to claim 1, characterized in that
said plurality of detectors comprise:a fifth detector comprising an
optical sensor for converting an electron beam into light and converting
the light into an electric signal; anda sixth detector comprising an
optical sensor for converting an electron beam into light and converting
the light into an electric signal,wherein said optical sensors in said
fifth detector and said sixth detector are disposed within said vacuum
chamber.

7. An inspecting apparatus according to claim 1, characterized in that:a
fifth detector comprising an optical sensor for converting an electron
beam into light and converting the light into an electric signal; anda
sixth detector comprising an optical sensor for converting an electron
beam into light and converting the light into an electric signal,wherein
at least one of said optical sensors in said fifth detector and said
sixth detector is disposed in the atmosphere.

8. An inspecting apparatus according to claim 6, characterized in that
said optical sensor of said fifth detector is a CCD sensor having a
plurality of pixels, and said optical sensor of said sixth detector is a
TDI sensor having a plurality of pixels.

9. An inspecting apparatus according to claim 1, characterized in that
said switching mechanism comprises at least one of:a moving mechanism for
mechanically moving one of said plurality of detectors to a position at
which said one detector does not prevent another one of said plurality of
detectors from receiving an electron beam; anda deflector for switching a
traveling direction of the electron beam to one of said plurality of
detectors and to another of said plurality of detectors.

10. An inspecting apparatus according to claim 1, characterized by
capturing a two-dimensional image.

11. An inspecting apparatus according to claim 1, characterized by
comprising an electron amplifier for amplifying the electron beam.

12. An inspecting apparatus according to claim 1, characterized by
comprising an electro-optical system such as a lens, wherein the
trajectory of the electron beam is controlled by said electro-optical
system.

13. An inspecting apparatus according to claim 12, characterized in that
said electro-optical system comprises a noise cut aperture.

14. An inspecting apparatus according to claim 12, characterized in that
said electro-optical system comprises a projection optical system.

15. An inspecting apparatus according to claim 1, characterized by
comprising an electron source for irradiating the sample with electrons.

16. An inspecting apparatus according to claim 1, characterized by
comprising an electromagnetic wave source for irradiating the sample with
an electromagnetic wave.

17. An inspecting apparatus according to claim 1, characterized by
comprising an electron source for irradiating the sample with electrons,
and an electromagnetic wave source for irradiating the sample with an
electromagnetic wave.

18. An inspecting apparatus according to claim 16, wherein said
electromagnetic wave source is capable of generating one of UV light, DUV
light, laser light, and X-ray.

19. A defect inspecting apparatus characterized by comprising the
inspecting apparatus according to claim 1.

20. A device manufacturing method characterized by inspecting a wafer for
defects halfway in a process by the defect inspecting apparatus according
to claim 19.

21. A defect inspecting apparatus comprising:a primary optical system
having an electron gun for emitting a primary electron beam for guiding
the primary electron beam to a sample; anda secondary optical system for
guiding a secondary electron beam emitted from the sample to a detection
system,characterized in that said detection system comprises:a first
EB-CCD sensor for adjusting the optical axis of an electron beam;an
EB-TDI sensor for capturing an image of the sample; anda second EB-CCD
sensor for evaluating a defective site based on the image captured by
said EB-TDI sensor.

22. A defect inspecting apparatus according to claim 20, characterized in
that said second EB-CCD sensor has a pixel size smaller than a pixel size
of said first EB-CCD sensor.

23. A defect inspecting method for inspecting a sample for defects in a
defect inspecting apparatus having a primary optical system for guiding
the primary electron beam to a sample, and a secondary optical system for
guiding a secondary electron beam emitted from the sample to a detection
system, characterized by:adjusting an optical axis using said EB-CCD
sensor;capturing an image of a sample using said EB-TDI sensor;specifying
a defective site on the sample from the image captured by said EB-TDI
sensor;capturing an image of the defective site on the sample using said
EB-CCD sensor; andcomparing the image of the defective site captured by
said EB-TDI sensor with the image of the defective site captured by said
EB-CCD sensor to determine a false defect or a true defect.

Description:

TECHNICAL FIELD

[0001]The present invention relates a detector for capturing electron
beams or optical signals. More particularly, the present invention
relates to an inspecting apparatus which has two or more detectors
disposed within a single barrel, one of which is selected in accordance
with the amount of electronic or optical signals or an S/N ratio, thereby
allowing for detection and measurement of images on the surface of a
sample.

[0002]With the use of this inspecting apparatus, a sample can be
efficiently inspected for evaluating the structure on the surface
thereof, observing the surface in enlarged view, evaluating the material
thereof, inspecting an electrically conductive state thereof, and the
like. Accordingly, the present invention relates to a method of
accurately and reliably inspecting highly dense patterns having a minimum
line width of 0.15 μm or less for defects at a high throughput, and a
device manufacturing method which involves inspecting patterns halfway in
a device manufacturing process.

BACKGROUND ART

[0003]A conventional inspecting apparatus switches a detector comprising
an electron sensor for detecting electrons and a detector comprising an
optical sensor for detecting light for use in detecting electrons or
light. Particularly, one detector is switched to the other as mentioned
above for capturing electrons or light emitted from the same object to
detect the amount of electrons or light and a changing amount thereof, or
capturing an image. For example, electron or light incident conditions
are adjusted on the basis of conditions detected by a CCD (charge coupled
device) based detector, followed by replacing the CCD detector with a TDI
(time delay integration) detector to make a high-speed inspection,
measurement, and the like of the object. Specifically, when the incident
conditions are adjusted using the TDI sensor, a low scaling factor of
image in the adjustments of the incident condition causes secondary
electrons from a sample to impinge and not impinge on some regions of a
MCP (micro-channel plate), which receives secondary electrons from a
sample, resulting in local damages to the MCP. For this reason, the
incident conditions are mainly adjusted using a CCD sensor.

[0004]An example of a conventional inspecting apparatus is shown in FIGS.
28 and 29. FIG. 28(A) shows a CCD inspecting apparatus 300. The CCD
inspecting apparatus 300 comprises a CCD sensor 301 and a camera 302
which are placed in the atmosphere. Secondary electrons emitted from a
sample (not shown) are amplified by an MCP 303 and then impinge on a
fluorescent plate 304 which converts the secondary electrons into an
optical signal representative of the image of the sample. The optical
signal output from the fluorescent plate 304 is converted by the optical
lens 306 placed in the atmosphere through a feed through 305 formed in a
vacuum chamber MC, and focused on the CCD sensor 301 to form the image of
the sample in the camera 302.

[0005]FIG. 28(B) in turn shows a TDI detector 310, where a TDI sensor 311
is placed within a vacuum chamber MC. A fluorescent plate 313 is disposed
in front thereof through light transmission means such as an FOP (fiber
optic plate) 3444 or the like, so that secondary electrons from a sample
enter the fluorescent plate 313 through the MCP 314, where the secondary
electrons are converted into an optical signal which is then transmitted
to the TDI sensor 311. An electric signal output from the TDI sensor 311
is transmitted to a camera 317 through a pin 316 provided in a feed
through unit 315.

[0006]Accordingly, in the case of FIG. 28, a change of the CCD detector
300 to the TDI detector 310 involves changing a unit of a flange and a
set of essential parts mounted thereon. Specifically, the inspecting
apparatus 300 is opened to the atmosphere, the flange, fluorescent plate
304, optical lens 306, and CCD sensor 301 are removed from the CCD
detector 300, and then the feed through flange 315, fluorescent late 313,
FOP 3444, TDI sensor 311, and camera 317 of the TDI detector 301 are
mounted in unit. For changing the TDI detector 310 with the CCD detector
300, the foregoing works are performed in the reverse procedure to the
above. In this regard, light or electrons emitted from a sample under
observation may be enlarged by an optical system, and the enlarged
electrons or light is amplified, followed by observation of the amplified
signal by a detector.

[0007]In FIGS. 29(A) and (B), in turn, MCPs 303, 314 and fluorescent
plates 304, 313 are disposed within a vacuum chamber MC. Therefore, in
the configuration shown in FIG. 29, when a change is made between a CCD
detector 300 and a TDI detector 310, elements placed in the atmosphere,
i.e., a set including an optical lens 306, a CCD sensor 301, and a camera
302 is changed with a set including a TDI sensor 311, a camera 317, and
an optical lens 318, or vice versa.

[0008]An apparatus for creating image data of a sample using a detection
result thus provided by a detector, and comparing the image data with
data on a die-by-die basis to inspect the sample for defects is known
(see JP-5-254140423 and JP-6-141416424 for the apparatus).

[0009]The conventional scheme as described above, when used, will require
not only an immense time for assembly, vacuum abandonment, adjustments
and the like involved in the change of the detector, but also works for
adjusting the alignment of the electron or optical axis, associated with
the change of the detector. For example, assuming that the TDI detector
310 is substituted for the CCD detector 300 for converting a secondary
electron beam into an optical signal within the vacuum chamber MC as
shown in FIG. 28, works such as stop of the apparatus, purging, opening
to the atmosphere, change of the detector, evacuation, breakdown
adjustment such as conditioning, adjustment of a beam axis, and the like
are performed in order, and a time required therefor amounts to 50 to 429
hours each time. Therefore, assuming that an electro-optical system is
adjusted and conditioned, for example, ten times a year, the foregoing
works are involved each time, thus resulting in 500 to 4290 hours
required therefor.

[0010]The configuration shown in FIG. 29 has been conventionally employed
for solving the problem inherent in FIG. 28. This configuration is
employed because the MCP 303, 314 and fluorescent plates 304, 313 are
disposed within the vacuum chamber MC as shown in FIG. 29, so that the
unit of the CCD sensor 301 and camera 302 can be readily changed to the
unit of the TDI sensor 311 and camera 317 in the atmosphere. However, a
problem arises in deterioration of MTF due to the feed through 305 which
is made of hermetic optical glass which cannot provide a wide viewing
field. As a result, the viewing field generally extends on the order of
1×1 to 10×10 mm at the position of the fluorescent plate, and
for providing a wider viewing field, it is necessary to prevent the
deterioration of the MFT due to a defective flatness and non-uniformity
of the optical glass and fluctuations in focus, and it is also necessary
to prevent deteriorations in MTF and luminance by providing an optical
lens which has a viewing field approximately five to six times wider. An
optical lens system which achieves this requires a highly accurate and
expensive lens, resulting in a cost 10 to 15 times higher, by way of
example. Further, since the optical system is increased in size by a
factor of 5 to 15, the resulting inspecting apparatus may be unavailable
if there are limitations to the height of the apparatus.

[0016]a primary optical system having an electron gun for emitting a
primary electron beam for guiding the primary electron beam to a sample;
and

[0017]a secondary optical system for guiding a secondary electron beam
emitted from the sample to a detection system, characterized in that the
detection system comprises:

[0018]a first EB-CCD sensor for adjusting the optical axis of an electron
beam;

[0019]an EB-TDI sensor for capturing an image of the sample; and

[0020]a second EB-CCD sensor for evaluating a defective site based on the
image captured by the EB-TDI sensor.

[0021]Further, the present invention provides a defect inspecting method
for inspecting a sample for defects in a defect inspecting apparatus
having a primary optical system for guiding the primary electron beam to
a sample, and a secondary optical system for guiding a secondary electron
beam emitted from the sample to a detection system. The defect inspecting
method is characterized by:

[0022]adjusting an optical axis using the EB-CCD sensor;

[0023]capturing an image of a sample using the EB-TDI sensor;

[0024]specifying a defective site on the sample from the image captured by
the EB-TDI sensor;

[0025]capturing an image of the defective site on the sample using the
EB-CCD sensor; and

[0026]comparing the image of the defective site captured by the EB-TDI
sensor with the image of the defective site captured by the EB-CCD sensor
to determine a false defect or a true defect.

[0027]As described above, the present invention disposes a plurality of
detectors within a vacuum chamber and can detect an electronic or an
optical signal using one of the detectors. A detector suitable for
electrons or light to be captured is selected in accordance with the
amount of signal, the S/N ratio and the like, and a signal is applied to
the selected detector to perform required detecting operations.

[0028]Advantageously, in this way, it is possible to not only save a time
taken to change one detector to another but also perform works such as
beam condition adjustments, inspection, measurement and the like by
immediately using an optimal detector when it is needed. Further, a
signal can be applied to the detector while minimizing degradations in
image quality without lower MTF or image distortions due to optical
lenses and lens systems. In this regard, the MTF and contrast are used as
indexes for the resolution.

[0029]For example, the surface of a sample can be inspected, measured, and
observed at high speeds by capturing a still image and adjusting the
optical axis using a CCD detector, and subsequently directing a beam into
a TDI detector to capture image without changing the detector, as has
been previously required.

[0030]In the past, detectors are change from one to another upon
adjustments to a variety of use conditions, so that the changing works
are generally performed approximately ten times a year on average.
Specifically, 1000 hours (10×100) have been spent for the changing
works every year, but according to the present invention, such a loss of
time can be reduced. Also, when a vacuum chamber is opened to the
atmosphere, particles and dust are likely to stick to the inner wall of
the vacuum chamber and parts within the vacuum chamber, but the present
invention can eliminate such a risk. Also, since parts in the vacuum
environment can be prevented from surface oxidization due to the exposure
to the atmosphere, voltages and magnetic flux generated from electrodes,
magnetic poles and the like can be used with stability without influences
of unstable operations possibly resulting from oxidized parts.
Particularly, in an aperture having a small diameter such as an NA
opening on which an electron beam impinges, it is thought that during the
exposure to the atmosphere, moisture and oxygen in the air stick to the
aperture to promote the sticking and production of contamination, but the
present invention solves such a problem.

[0031]For adjusting an electro-optical system for guiding an electron beam
generated from the surface of a sample such as a wafer to a detector,
signals often concentrate on a sensor. In other words, the sensor
simultaneously includes an area which exhibits a higher signal strength
and an area which exhibits a lower signal strength. As a result, if the
area of higher signal strength is damaged, the sensor is rendered
non-uniform in sensitivity. If an inspection or a measurement is made
using such a sensor which is non-uniform in sensitivity, the result of
the measurement involves large variations because a smaller signal
representative of an image is captured in the non-uniform area, leading
to a false defect. Even if the intensity of incident electrons or the
like is uniform, an output signal from a damaged area varies in strength,
resulting in a non-uniform sensor output. It is thought that erroneous
measurements can be made due to such non-uniform output of the sensor.
Such a problem can be solved by the present invention.

[0032]In the inspecting apparatus according to the present invention, a
beam irradiated to a sample may be an electron beam or light such as UV
light, DUV light, laser light or the like, or a combination of an
electron beam and light. Any of reflected electrons, secondary electrons,
back scattered electrons, and Auger electrons may be used for the
electron beams to capture a required image. When using light such as UV
light, DUV light, laser light or the like, an image is detected by
optical electrons. It is also possible to detect defects on the surface
of a sample using scattered light which occurs when such light is
irradiated to the surface of the sample. A quartz fiver or a hollow fiber
can be used to efficiently introduce light such as UV light, DUV light,
laser light or the like onto the surface of the sample.

[0033]When a combination of an electron beam and light is used for
irradiating the surface of a sample therewith, it is possible to solve a
problem of the inability to uniformly irradiate the sample with electrons
due to charge-up which causes a change in the potential on the surface
when an electron beam alone is used. Accordingly, by using light which
can be irradiated irrespective of the potential on the surface, electrons
can be stably and efficiently captured from the surface of the sample for
use in image capturing. For example, when the sample is irradiated with
UV light, not only optical electrons are generated, but also a number of
electrons are excited to a metastable state, so that free electrons are
increased when an electron beam is irradiated thereto, resulting in an
efficient emission of secondary electrons.

[0034]Semiconductor devices can be manufactured at a high throughput and
with a high yield rate by applying the inspecting apparatus according to
the present invention to an inspection of wafers for defects halfway in a
manufacturing process.

[0038]A front elevation showing main components of an inspecting apparatus
which is one embodiment of a charged particle beam apparatus according to
the present invention, viewed along a line A-A in FIG. 1-3.

[0104]FIGS. 29(A) and 29(B) are diagrams for describing a conventional
inspecting apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

[0105]First, the general configuration of a semiconductor inspection
system will be described with reference to FIG. 1-1. The semiconductor
inspection system comprises an inspecting apparatus, a power supply rack,
a control rack, an image processing rack, a deposition apparatus, an
etching apparatus, and the like. Roughing vacuum pumps such as a dry pump
are installed outside of a clean room. Main components within the
inspecting apparatus comprises an electron beam vacuum chamber, a vacuum
transfer system, a main housing which contains a stage, a vibration
isolator, turbo molecular pump, and the like.

[0106]When viewing the inspection system from a functional standpoint, the
electron beam vacuum chamber is mainly composed of an electro-optical
system, a detection system, an optical microscope, and the like. The
electro-optical system is composed of an electron gun, lenses and the
like, while the transfer system is composed of a vacuum transfer robot,
an atmosphere transfer robot, a cassette loader, a variety of position
sensors, and the like.

[0107]The deposition apparatus, etching apparatus, and washing apparatus
(not shown) may be installed side by side near the inspecting apparatus
or incorporated in the inspecting apparatus. They are used, for example,
to prevent a sample from being charged, or to clean the surface of the
sample. A sputter scheme, when used, can provide both functions of
deposition and etching.

[0108]Thought not shown, in some applications, associated apparatuses may
be installed side by side near the inspecting apparatus, or these
associated apparatuses may be incorporated in the inspecting apparatus
for use therewith. Alternatively, these associated apparatuses may be
incorporated in the inspecting apparatus. For example, a chemical
mechanical polishing apparatus (CMP) and a washing apparatus may be
incorporated in the inspecting apparatus, or alternatively, a CVD
(chemical vacuum deposition) apparatus may be incorporated in the
inspecting apparatus, in which case the area required for installation,
and the number of units for transferring samples can be saved, a transfer
time can be reduced, and other advantages can be provided. Likewise, a
deposition apparatus such as a plating apparatus may be incorporated in
the inspecting apparatus. Also, the inspecting apparatus can be used in
combination with a lithography apparatus in a similar manner.

[0109]In the following, one embodiment of an inspecting apparatus
according to the present invention will be described with reference to
the drawings, as a semiconductor inspecting apparatus for inspecting a
substrate or a wafer formed with patterns on the surface thereof as an
object under inspection.

[0110]Main components of the semiconductor inspecting apparatus of this
embodiment are shown in front elevation and plan view in FIGS. 1-2 and
1-3. The semiconductor inspecting apparatus 400 of this embodiment
comprises a cassette holder 401 for holding a cassette which stores a
plurality of wafers W; a mini-environment device 402; a main housing 403
which defines a working chamber; a loader housing 404 disposed between
the mini-environment device 402 and main housing 403 for defining two
loading chambers; a loader 406 for loading a wafer from the cassette
holder 401 onto the stage device 405 disposed within the main housing
403; and an electro-optical system 407 attached to the vacuum housing.
These components are laid out in a positional relationship as illustrated
in FIGS. 1-2 and 1-3.

[0111]The semiconductor inspecting apparatus 400 also comprises a
pre-charge unit 408 disposed in the main housing 403 in vacuum; a
potential application mechanism (not shown) for applying a potential to a
wafer W; an electron beam calibration mechanism (described later with
reference to FIG. 1-7), and an optical microscope 410 which forms part of
an alignment controller 409 for positioning a wafer W on the stage
device.

[0112]The cassette holder 401 is configured to hold a plurality (two in
this embodiment) of cassettes c (for example, closed cassettes such as
SMIF, FOUP manufactured by Assist Co.) in which a plurality (for example,
twenty-five) wafers W are placed side by side in parallel, oriented in
the vertical direction. In this embodiment, the cassette holder 401 is a
type adapted to automatically load the cassette c, and comprises, for
example, an up/down table 411, and an elevating mechanism 444 for moving
the up/down table 411 up and down. The cassette c can be automatically
set on the up/down table 411 in a state indicated by chain lines in FIG.
1-3. After the setting, the cassette c is automatically rotated to a
state indicated by solid lines in FIG. 1-3 so that it is directed to the
axis of pivotal movement of a first carrier unit within the
mini-environment chamber.

[0113]It should be noted that substrate or wafers accommodated in the
cassette c are subjected to an inspection which is generally performed
after a process for processing the wafers or in the middle of the process
within semiconductor manufacturing processes. Specifically, accommodated
in the cassette are wafers which have undergone a deposition process,
CMP, ion implantation and so on; wafers formed with wiring patterns on
the surface thereof; or wafers which have not been formed with wiring
patterns. Since a large number of wafers accommodated in the cassette c
are spaced from each other in the vertical direction and arranged side by
side in parallel, and the first carrier unit has an arm which is
vertically movable, a wafer at an arbitrary position can be held by the
first carrier unit which will be described later in detail.

[0114]In FIGS. 1-2 and 1-5, the mini-environment device 402 comprises a
housing 414 defining a mini-environment space 413 that is controlled for
the atmosphere; a gas circulator 415 for circulating a gas such as clean
air within the mini-environment space 413 to execute the atmosphere
control; a discharger 416 for recovering a portion of air supplied into
the mini-environment space 413 to discharge the same; and a prealigner
417 for roughly aligning a sample, i.e., a wafer placed in the
mini-environment space 413. The housing 414 has a top wall 418, bottom
wall 419, and peripheral wall 420 which surrounds four sides of the
housing 414, to provide a structure for isolating the mini-environment
space 413 from the outside. Also, a sensor may be provided within the
environment space for observing the cleanness such that the apparatus can
be shut down when the cleanness exacerbates.

[0115]An access port 421 is formed in a portion of the peripheral wall 87
of the housing 414 that is adjacent to the cassette holder 401. A shutter
device of a known structure may be provided near the access port 421 for
closing the access port 421 from the mini-environment device side. An air
supply unit may not be provided within the mini-environment space but
outside thereof.

[0116]The discharger 416 comprises a suction duct 422 disposed at a
position below the wafer carrying surface of the carrier unit and below
the carrier unit; a blower 423 disposed outside the housing 414; and a
conduit 424 for connecting the suction duct 422 to the blower 423. The
discharger 416 aspires a gas flowing down around the carrier unit and
including particle, which could be produced by the carrier unit, through
the suction duct 422, and discharges the gas outside the housing 414
through the conduit 424 and the blower 423.

[0117]The prealigner 417 disposed within the mini-environment space 413
optically or mechanically detects an orientation flat (which refers to a
flat portion formed along the outer periphery of a circular wafer and
hereinafter called as orientation flat) formed on the wafer, or one or
more V-shaped notches formed on the outer peripheral edge of the wafer,
and previously aligns the position of the wafer in a rotating direction
about the axis O-O at an accuracy of approximately tone degree. The
prealigner is responsible for a rough alignment of the wafer.

[0118]In FIGS. 1-2 and 1-3, the main housing 403, which defines a working
chamber 426, comprises a housing body 427 that is supported by a housing
supporting device 430 carried on a vibration blocking device, i.e.,
vibration isolator 429 disposed on a base frame 428. The housing
supporting device 430 comprises a frame structure 431 assembled into a
rectangular form. The housing body 427 comprises a bottom wall 432
mounted on and securely carried on the frame structure 431; a top wall
433; and a peripheral wall 434 which is connected to the bottom wall 432
and the top wall 433 and surrounds four sides of the housing body 427,
and isolates the working chamber 426 from the outside.

[0119]In this embodiment, the housing body and the housing supporting
device 430 are assembled into a rigid construction, and the vibration
isolator 429 blocks vibrations from the floor, on which the base frame
428 is installed, from being transmitted to the rigid structure. A
portion of the peripheral wall 434 of the housing 427 that adjoins the
loader housing 404 is formed with an access port 435 for introducing and
removing a wafer therethrough. The working chamber 426 is kept in a
vacuum atmosphere by a vacuum device (not shown) of a known structure. A
controller 2 is disposed below the base frame 428 for controlling the
operation of the overall apparatus.

[0120]In FIGS. 1-2, 1-3, and 1-6, the loader housing 404 comprises a
housing body 438 which defines a first loading chamber 436 and a second
loading chamber 438. The housing body 438 comprises a bottom wall 439; a
top wall 440; a peripheral wall 441 which surrounds four sides of the
housing body 438; and a partition wall 442 for partitioning the first
loading chamber 436 and the second loading chamber 438 to isolate the two
loading chambers from the outside. The partition wall 442 is formed with
an aperture, i.e., an access port 443 for passing a wafer W between the
two loading chambers. Also, a portion of the peripheral wall 441 that
adjoins the mini-environment device 402 and the main housing 403, is
formed with access ports 444 and 445. The housing body 438 of the loader
housing 404 is carried on and supported by the frame structure 431 of the
housing supporting device 430. This prevents the vibrations of the floor
from being transmitted to the loader housing 404 as well.

[0121]The access port 444 of the loader housing 404 is in alignment with
the access port 446 of the housing 414 of the mini-environment device
402, and a shutter device 447 is provided for selectively blocking a
communication between the mini-environment space 413 and the loading
chamber 436. Likewise, the access port 445 of the loader housing 404 is
in alignment with the access port 435 of the housing body 427, and a
shutter device 448 is provided for selectively blocking a communication
between the loading chamber 438 and the working chamber 426 in a hermetic
manner.

[0122]Further, the opening formed through the partition wall 442 is
provided with a shutter device 450 for closing the opening with a door
449 to selectively block a communication between the first and second
loading chambers in a hermetic manner.

[0123]Within the first loading chamber 436, a wafer rack 451 is disposed
for supporting a plurality (two in this embodiment) of wafers spaced in
the vertical direction and maintained in a horizontal state. The loading
chambers 436, 438 are controlled for the atmosphere to be maintained in a
high vacuum state (at a vacuum degree of 10-5 to 10-6 Pa) by a
vacuum evacuator (not shown) in a conventional structure including a
vacuum pump, not shown. In this event, the first loading chamber 436 may
be held in a low vacuum atmosphere as a low vacuum chamber, while the
second loading chamber 438 may be held in a high vacuum atmosphere as a
high vacuum chamber, to effectively prevent contamination of wafers. The
employment of such a loading housing structure including two loading
chambers allows a wafer W to be carried, without significant delay from
the loading chamber the working chamber. The employment of such a loading
chamber structure provides for an improved throughput for the defect
inspection, and the highest possible vacuum state around the electron
source which is required to be kept in a high vacuum state.

[0124]The first and second loading chambers 436, 438 are connected to
vacuum pumping pipes and vent pipes for an inert gas (for example, dried
pure nitrogen) (neither of which are shown), respectively. In this way,
the atmospheric state within each loading chamber is attained by an inert
gas vent (which injects an inert gas to prevent an oxygen gas and so on
other than the inert gas from attaching on the surface).

[0125]In the inspecting apparatus of the present invention which uses
electron beams, when representative lanthanum hexaboride (LaB6) used
as an electron source for an electro-optical system is once heated to
such a high temperature that causes emission of thermal electrons, it is
critical that it is not exposed to oxygen within the limits of
possibility so as not to shorten the lifetime. However, by carrying out
the atmosphere control as mentioned above at a stage before introducing
the wafer into the working chamber in which the electro-optical system is
disposed, the foregoing can be more certainly carried out.

[0126]The stage device 405 comprises a fixed table 452 disposed on the
bottom wall 432 of the main housing 403; a Y-table 453 movable in a Y
direction on the fixed table (the direction vertical to the drawing sheet
in FIG. 1-2); an X-table 454 movable in an X direction on the Y-table 453
(in the left-to-right direction in FIG. 1-2); a turntable 455 rotatable
on the X-table; and a holder 456 disposed on the turntable 455. A wafer W
is releasably held on a wafer carrying surface 551 of the holder 456. The
holder may be of a known structure which is capable of releasably
chucking a wafer by means of a mechanical or electrostatic chuck feature.

[0127]The stage device 405 uses servo motors, encoders and a variety of
sensors (not shown) to operate the plurality of tables 453-455 mentioned
above to permit highly accurate alignment of a wafer W held on the
carrying surface 130 by the holder 456 in the X direction, Y direction
and Z-direction (the Z-direction is the up-down direction in FIG. 1-2)
with respect to electron beams irradiated from the electro-optical
system, and in a direction (θ direction) about the axis normal to
the wafer supporting surface. In this regard, the alignment in the
Z-direction may be made such that the position on the carrying surface of
the holder, for example, can be finely adjusted in the Z-direction. In
this event, a reference position on the carrying surface is sensed by a
position measuring device using a laser of an extremely small diameter (a
laser interference range finder using the principles of interferometer)
to control the position by a feedback circuit, not shown. Additionally or
alternatively, the position of a notch or an orientation flat of a wafer
is measured to sense a plane position or a rotational position of the
wafer relative to the electron beam to control the position of the wafer
by rotating the turntable by a stepping motor which can be controlled in
extremely small angular increments.

[0128]In order to maximally prevent particle produced within the working
chamber 426, servo motors 131, 132 and encoders 133, 134 for the stage
device 405 are disposed outside the main housing 403.

[0129]It is also possible to establish a basis for signals which are
generated by previously inputting a rotational position, and
X-Y-positions of a wafer relative to the electron beams in a signal
detecting system or an image processing system, later described.

[0130]The loader 406 comprises a robot-based first carrier unit 462
disposed in the housing 414 of the mini-environment device 402, and a
robot-based second carrier unit 463 disposed in the second loading
chamber 438.

[0131]The first carrier unit 462 has a multi-node arm 465 for rotation
about an axis O1-O1 relative to a driver 464. While an
arbitrary structure may be applied to the multi-node arm, this embodiment
employs the multi-node arm 465 which has three parts attached for
rotation relative to each other. A part of the arm 465 of the first
carrier unit 462, i.e., a first part closest to the driver 464 is
attached to a shaft 466 which can be rotated by a driving mechanism (not
shown) in a general-purpose structure arranged in the driver 464. The arm
465 is rotatable about the axis O1-O1 by the shaft 466, and is
telescopical in a radial direction relative to the axis O1-O1
as a whole through relative rotations among the parts. At the leading end
of the third part furthest away from the shaft 466 of the arm 465, a
chuck 467 is attached for chucking a wafer, such as a mechanical chuck in
a general-purpose structure, an electrostatic chuck or the like. The
driver 464 is vertically movable by an elevating mechanism 468 in a
general-purpose structure.

[0132]In this first carrier unit 462, the arm 465 extends toward one of
two cassettes c held in the cassette holder 10 in a direction M1 or M2,
and a wafer W stored in the cassette c is carried on the arm, or is
chucked by the chuck (not shown) attached at the leading end of the arm
for removal. Subsequently, the arm is retracted (to the state illustrated
in FIG. 1-3), and the arm is rotated to a position at which the arm can
extend toward the pre-aligner 417 in a direction M3, and is stopped at
this position. Then, the arm again extends to the pre-aligner 417 to
transfer the wafer held by the arm thereto. After receiving the wafer
from the pre-aligner 417 in a manner reverse to the foregoing, the arm is
further rotated and stopped at a position at which the arm can extend
toward the first loading chamber 436 (in a direction M4), where the wafer
is passed to a wafer receiver 451 within the first loading chamber 436.

[0133]It should be noted that when a wafer is mechanically chucked, the
wafer should be chucked in a peripheral zone (in a range approximately 5
mm from the periphery). This is because the wafer is formed with devices
(circuit wires) over the entire surface except for the peripheral zone,
so that if the wafer were chucked at a portion inside the peripheral
zone, some devices would be broken or defects would be produced.

[0134]The second carrier unit 463 is basically the same as the first
carrier unit 462 in structure, and differs only in that the second
carrier unit 463 carries a wafer W between the wafer rack 451 and the
carrying surface of the stage device 405.

[0135]In the loader 406 described above, the first and second carrier
units 462, 463 carry wafers from the cassette c held in the cassette
holder onto the stage device 405 disposed in the working chamber 426 and
vice versa while holding the wafer substantially in a horizontal posture.
Then, the arms of the carrier units 462, 463 are moved up and down only
when a cassette is extracted from the cassette c and loaded into the
same, when a wafer is placed on the wafer lack and is extracted from the
same, and when a wafer is placed on the stage device 405 and removed from
the same. Therefore, the carrier units 462, 463 can smoothly move even a
large wafer which may have a diameter of, for example, 30 cm.

[0136]Next, a description will be made in order of the transfer of a wafer
from the cassette c supported by the cassette holder 401 to the stage
device 405 disposed in the working chamber 426. In this embodiment, as
the cassette c is set on the up/down table 411, the up/down table 411 is
moved down by the elevating mechanism 412 to bring the cassette c into
alignment to the access port 421. As the cassette c is in alignment to
the access port 421, a cover (not shown) disposed on the cassette c is
opened, whereas a cylindrical cover is arranged between the cassette c
and the access port 421 of the mini-environment device 402 to block the
cassette c and mini-environment space 402 from the outside. When the
mini-environment device 402 is equipped with a shutter device for
opening/closing the access port 421, the shutter device is operated to
open the access port 421.

[0137]On the other hand, the arm 465 of the first carrier unit 462 remains
oriented in either the direction M1 or M2 (in the direction M1 in this
description), and extends to receive one of wafers stored in the cassette
c with its leading end as the access port 421 is opened.

[0138]Once the arm 465 has received a wafer, the arm 465 is retracted, and
the shutter device (if any) is operated to close the access port 421.
Then, the arm 465 is rotated about the axial line O1-O1 so that
it can extend in the direction M3. Next, the arm 465 extends to transfer
the wafer carried on the leading end thereof or chucked by a chuck onto
the pre-aligner 417 which determines a direction in which the wafer is
rotated (direction about the center axis perpendicular to the surface of
the wafer) within a predetermined range. Upon completion of the
positioning, the first carrier unit 462 retracts the arm 465 after the
wafer is received from the pre-aligner 417 to the leading end of the arm
465, and takes a posture in which the arm 465 can be extended in the
direction M4. Then, the door 469 of the shutter device 447 is moved to
open the access ports 226, 436, permitting the arm 465 to place the wafer
on the upper shelf or lower shelf of the wafer rack 451 within the first
loading chamber 436. It should be noted that before the shutter device
447 opens the access ports to pass the wafer to the wafer rack 451, the
opening 443 formed through the partition 442 is hermetically closed by
the door 449 of the shutter device 450.

[0139]In the wafer transfer process by the first carrier unit 462, clean
air flows in a laminar state (as a down flow) from the gas supply unit
231 disposed in the housing body 414 of the mini-environment device 402,
for preventing dust from sticking to the upper surface of the wafer
during the transfer. Part of air around the carrier unit is aspired from
the suction duct 422 of the discharger 416 for emission out of the
housing body 414. The remaining air is recovered through the recovery
duct 89 arranged on the bottom of the housing body 414, and again
returned to the gas supply unit 470.

[0140]As a wafer is placed on the wafer rack 451 within the first loading
chamber 436 of the loader housing 404 by the first carrier unit 462, the
shutter device 447 is closed to hermetically close the loading chamber
436. Then, the loading chamber 436 is brought into a vacuum atmosphere by
expelling the air within the loading chamber 436, filling an inert gas in
the loading chamber 436, and then discharging the inert gas. The vacuum
atmosphere in the loading chamber 436 may have a low degree of vacuum. As
the degree of vacuum has reached a certain level in the loading chamber
436, the shutter device 450 is operated to open the access port 442,
which has been hermetically closed by the door 449, and the arm 472 of
the second carrier unit 463 extends to receive one wafer from the wafer
receiver 451 with the chuck at the leading end thereof (placed on the
leading end or chucked by a chuck attached to the leading end). As the
wafer has been received, the arm 472 is retracted, and the shutter device
450 is again operated to close the access port 443 with the door 449.

[0141]It should be noted that before the shutter device 450 opens the
access port 443, the arm 472 has previously taken a posture in which it
can extend toward the wafer rack 451 in a direction N1. Also, as
described above, before the shutter device 450 opens the access port 443,
the shutter device 448 closes the access ports 445, 435 with the door 473
to block communications between the second loading chamber 438 and the
working chamber 426, and the second loading chamber 438 is evacuated.

[0142]As the shutter device 450 closes the access port 443, the second
loading chamber 438 is again evacuated to a degree of vacuum higher than
that of the first loading chamber 436. In the meantime, the arm 465 of
the second carrier unit 462 is rotated to a position from which the arm
465 can extend toward the stage device 405 within the working chamber
426. On the other hand, in the stage device 405 within the working
chamber 426, the Y-table 202 is moved upward, as viewed in FIG. 13, to a
position at which the center line X0-X0 of the X-table 203
substantially matches an X-axis line X1-X1 which passes the
axis of rotation O2-O2 of the second carrier unit 463. Also,
the X-table 203 has moved to a position close to the leftmost position,
as viewed in FIG. 1-3, and is waiting at this position.

[0143]When the degree of vacuum in the second loading chamber 438 is
increased to a level substantially identical to that of the working
chamber 426, the door 473 of the shutter device 448 is moved to open the
access ports 445, 435, and the arm extends so that the leading end of the
arm, which holds a wafer, approaches the stage device 405 within the
working chamber 426. Then, the wafer W is placed on the carrying surface
130 of the stage device 405. Once the wafer W has been placed on the
stage device 405, the arm is retracted, and the shutter device 448 closes
the access ports 445, 435.

[0144]The foregoing description has been made on the operation until a
wafer in the cassette c is carried and placed on the stage device. For
returning a wafer, which has been carried on the stage device and
processed, from the stage device into the cassette c, the operation
reverse to the foregoing is performed. Since a plurality of wafers are
stored in the wafer rack 451, the first carrier unit can carry a wafer
between the cassette and the wafer rack while the second carrier unit is
carrying a wafer between the wafer rack and the stage device, so that the
inspecting operation can be efficiently carried out.

[0145]FIGS. 1-7(A) and (B) are diagrams showing an exemplary electron beam
calibration mechanism. The electron beam calibration mechanism 480
comprises a plurality of Faraday cups 482, 483 disposed at a plurality of
positions on the side of the wafer W placement face 481 on the turntable
455 (FIG. 1-2). The respective Faraday cups are provided to measure a
beam current, where the Faraday cup 482 is used for a fine beam of
approximately 2 μmφ, for example, while the Faraday cup 483 is
used for a thick beam of approximately 30 μmφ, for example. The
Faraday cup 482 for thin beam measures a beam profile by moving the
turntable 455 in steps, while the Faraday cup 483 for thick beam measures
the total current amount of beam. The Faraday cups 482, 483 are disposed
such that their top surfaces are at the same level as the top surface of
the wafer W placed on the placement face 481. In this way, primary
electron beams emitted from the electron gun is monitored at all times.
This is because the electron gun cannot always emit a consistent electron
beam but varies the amount of electron beam emitted therefrom as it is
used.

[0146]FIG. 2 is a diagram showing the general configuration of an
electro-optical system in the inspecting apparatus together with a
positional relationship between a sample and a detection system. The
electro-optical system is disposed in a vacuum chamber, and comprises a
primary electro-optical system (hereinafter simply called the "primary
optical system") PR for emitting a primary electron beam which is guided
to a sample SL for irradiation to the sample SL; and a secondary
electro-optical system (hereinafter simply called the "secondary optical
system") SE for guiding secondary electron beams emitted from the sample
SL to a detection system DT. The primary optical system PR, which is an
optical system for irradiating an electron beam onto the surface of the
sample SL under inspection, comprises an electron gun 1 for emitting an
electron beam; a lens system 2 comprised of an electrostatic lens for
converging the primary electron beam emitted from the electron gun 1; a
When filter or ExB separator 3; and an objective lens system 4, where the
optical axis of the primary electron beam emitted from the electron gun 1
is inclined with respect to an irradiation optical axis of the electron
beam (perpendicular to the surface of the sample) which is irradiated to
the sample SL. An electrode 5 is disposed between the objective lens
system 4 and sample SL. This electrode 5 is in a shape axially symmetric
to the irradiation optical axis of the primary electron beam, and has its
voltage controlled by a power supply 6.

[0147]The secondary optical system SE comprises a lens system 7 comprised
of electrostatic lenses for passing therethrough secondary electrons
separated from the primary optical system by the ExB separator 3. This
lens system 7 functions as an enlarging lens for enlarging a secondary
electron image. The detection system DT comprises a detection unit 8
disposed on a focusing plane of the lens system 7, and an image
processing unit 9.

[0148]The present invention relates to improvements on a detection unit in
the inspecting apparatus as described above, and will be described below
in greater detail in connection with embodiments of the inspecting
apparatus according to the present invention with reference to the
drawings. Throughout all drawings, the same reference numerals refer to
the same or similar components.

[0149]FIG. 3 is a diagram schematically showing a first embodiment of the
inspecting apparatus according to the present invention, which comprises
a detector having an electron sensor and a detector having an optical
sensor both contained in a single chamber. In FIG. 3, a CCD detector 11
and a TDI detector 12 are disposed within a vacuum chamber MC such that
an EB-CCD (electron bombardment charge coupled device) sensor 13 of the
CCD detector 11 is positioned closer to a sample. In FIG. 3, the CCD
detector 11 and TDI detector 12 have their electron incident plane
perpendicular to the drawing. The EB-CCD sensor 13 is supported such that
it can be translated in the left-to-right direction in the figure by a
moving mechanism M disposed outside of the vacuum chamber MC. In this
way, the EB-CCD sensor 13 can be selectively moved to a position at which
it receives an electron beam e, and to a position at which it directly
applies the electron beam e into the TDI detector 12, thus making it
possible to selectively use the CCD detector 11 and TDI detector 12.
Here, the moving mechanism M moves the EB-CCD sensor to a position at
which the optical axis to the EB-CCD sensor, the optical axis to lens
conditions (lens intensity, beam deflection condition), and the lens
conditions (lens intensity, beam deflection condition) match, when the
EB-CCD sensor is moved to the position at which it receives an electron
beam. This positioning condition can be mechanically modified by
capturing images generated by the EB-CCD and EB-TDI for a sample having a
known pattern. Though not shown, the CCD detector 11 comprises a camera
connected to the EB-CCD sensor 13, a controller, a frame grabber board, a
PC and the like, to capture the output of the EB-CCD sensor 13, display
images, and control the CCD detector 11.

[0150]The EB-CCD sensor 13, which comprises a plurality of pixels which
are two-dimensionally arranged, receives the electron beam e emitted from
a sample and outputs a signal representative of a two-dimensional image
of the sample. The EB-CCD sensor 13, when the electron beam is directly
incident thereon, provides a gain corresponding to the energy of the
incident electron beam, i.e., electrons are amplified to accomplish the
accumulation of charges, and the charges are read at intervals of defined
time (for example 33 Hz) and output as an electric signal of a
two-dimensional image of one frame. For example, the EB=CCD sensor 13
used herein has pixels of 650 (horizontal direction)×485 (vertical
direction), a pixel size of 14 μm×14 μm, a frame acquisition
frequency of 33 Hz, and a gain of 100-1000. In this event, the gain of
the EB-CCD sensor 13 is dominated by the energy of incident electrons,
and can provide the gain of 300, for example, when the incident energy is
4 keV. The gain can be adjusted by the structure of the EB-CCD sensor 13.

[0151]The TDI detector 12, in turn, comprises an MCP 14 for amplifying an
electron beam e emitted from a sample; a fluorescent plate 15 for
receiving the amplified electron beam for conversion into light; an FOP
16 for transmitting the light generated from the fluorescent plate 15;
and a TDI sensor 17 for receiving an optical signal from the FOP 16. The
output of the TDI sensor 17 is transmitted to the camera 19 through the
pin 18, as swoon in FIG. 28(B). It should be noted that the MCP 14 is
disposed when electrons must be amplified, and may be omitted in some
cases.

[0152]The MCP 14, fluorescent plate 15, FOP 16, and TDI sensor 17 are
formed into a single package, where output pins of the TDI sensor 17 is
connected to pins 18 of the field through unit FT by wire bonding or
another connection means. With the TDI sensor 17 operating at high speeds
to provide a large number of pixels, a large number of pins 18 are
required, for example, 100 to 1000 pines as the case may be. The camera
19 inputs and outputs image signals in accordance with control signals
for image capturing. Though not shown, other than the camera 19, the
inspecting apparatus is provided with a power supply and a controller for
the camera 19, and an image processing system for capturing and
processing an image signal from the camera 19. An image evaluation value
can be calculated by processing image data generated by the image
processing system, and, for example, when used in a defect inspection,
sites of defects, type of defects, size of defects and the like can be
extracted and displayed on a screen.

[0153]A moving mechanism M is provided outside of the vacuum chamber M for
selectively implementing a case where the CCD detector 11 is used and a
case where the TDI detector 12 is used, and mechanically coupled to the
EB-CCD sensor 13. When the CCD detector 11 is used to align the optical
axes of the EB-CCD sensor and EB-TDI sensor, and adjust the lens
condition, the moving mechanism M is operated to move the EB-CCD sensor
13 such that its center comes to the position of the optical axis of the
electron beam e. In this state, the electron beam e can be sent into the
EB-CCD sensor 13 to generate an image signal representative of a
two-dimensional image of the sample. When the TDI detector 12 is used
after the completion of adjustments to the optical axes and the like, the
EB-CCD sensor 13 is moved by the moving mechanism M to a place away from
the optical axis of the electro-optical system, for example, to a place
spaced by a distance (for example, approximately 5 to 300 mm) at which
the EB-CCD sensor 13 does not affect an electron image and an electron
trajectory. In this way, the electron beam e is incident on the MCP 14 of
the TDI detector 12 without being impeded by the EB-CCD sensor 13. In
this regard, a shield is preferably provided for preventing charge-up at
a junction at which the moving mechanism M is coupled to the EB-CCD
sensor 13 (described later). The provision of such a mechanism eliminates
the need for the TDI in the adjustments of the optical axes and the like,
so that the MCP is prevented from being locally damaged. In addition,
since the EB-CCD sensor and EB-TDI sensor are disposed within the same
vacuum chamber, it is not necessary to break the vacuum atmosphere to
change the EB-CCD sensor with the EB-TDI sensor.

[0154]Also, since the EB-CCD sensor is operated when adjustments are made
to the optical axes and the like, the EB-CCD sensor and EB-TDI sensor may
be operated for the first one of wafers accommodated in a cassette, and
the EB-TDI sensor alone may be operated for the remaining wafers.
Alternatively, the EB-CCD sensor may be operated every predetermined
number of wafers to readjust the optical axes and the like.

[0155]FIG. 4 is a diagram schematically showing a second embodiment of an
inspecting apparatus according to the present invention. The moving
mechanism M shown in FIG. 3 can simply translate in one axial direction
(for example, in the X-direction). Instead, in the second embodiment
shown in FIG. 4, the moving mechanism M is configured to be movable in
three axial directions (X-, Y-, and Z-directions), to finely adjust the
center of the EB-CCD sensor 13 with respect to the center of the optical
axis of the electro-optical system. In this regard, an electron
deflection mechanism may be provided in front of the EB-sensor 13 (closer
to a sample) to adjust the position of the electron beam in order to
adjust the optical axis of the electro-optical system.

[0156]FIGS. 5(A)-5(C) schematically shown a third embodiment of an
inspecting apparatus according to the present invention, where (A) is a
view taken from the front, and (B) and (C) are views taken from one side.
As shown, the moving mechanism M in this embodiment utilizes rotational
movements rather than movements in one axial or three axial directions.
It should be noted that the TDI detector 12 does not comprise the MCP
because the electron amplification is not needed in this embodiment.

[0157]In FIG. 5(A), one end of a rotary shaft 21 is coupled to one end of
a flat EB-CCD sensor 13 which contains required circuits, substrates and
the like, while the other end of the rotary shaft 21 is coupled to the
moving mechanism M. FIGS. 5(B) and 5(C) are views of the configuration
shown in FIG. 5(A), taken from the side closer to the moving mechanism M.
When the CCD detector 11 is used, the EB-CCD sensor 13 is moved such that
the sensor plane thereof is perpendicular to the electron beam e, thus
causing the electron beam e to be incident on the EB-CCD sensor 13. When
the TDI detector 12 is used, the rotary shaft 21 is rotated by the moving
mechanism M, as shown in (C) to move the EB-CCD sensor 13 such that it is
in parallel with the optical axis of the electro-optical system. As such,
the electron beam e is incident on the fluorescent plate 15 which
converts the electron beam e into an optical signal which is then
incident on the TDI sensor 17 through the FOP 16.

[0158]The moving mechanism shown in FIG. 5, which utilizes the rotation,
can be advantageously reduced in size and weight, for example, by a
factor of two to ten, as compared with the moving mechanism described in
connection with FIGS. 3 and 4, which utilizes movements in one or three
axial direction.

[0159]FIG. 6 is a diagram schematically showing a fourth embodiment of an
inspecting apparatus according to the present invention, where two EB-TDI
sensors are provided instead of the single EB-CCD sensor in the first and
third embodiments, such that one can be selected from these EB-CCD
sensors and the TDI detector 12. Specifically, a moving mechanism M is
coupled to two EB-CCD sensors 131, 132 which differ in performance. For
example, the EB-CCD sensor 131 has pixels the size of which is
14×14 μm, while the EB-CCD sensor 132 has pixels, the size of
which is 7×7 μm, and these EB-CCD sensors have different
electron image resolutions in accordance with their larger and smaller
pixel sizes. In other words, an image generated by the EB-CCD sensor
having the smaller pixel size (7 μm) achieves a resolution twice or
more higher than that generated by the EB-CCD sensor having the larger
pixel size (14 μm) in providing an electron image. In this regard, the
number of EB-CCD sensors is not limited to two, but three or more EB-CCD
sensors may be provided as required.

[0160]The inspecting apparatus which comprise the three components, i.e.,
the EB-CCD sensor 131, EB-CCD sensor 132, and TDI detector 12 placed in
the same vacuum chamber M may be used, by way of example, in the
following manner. Assuming that the EB-CCD sensor 131 has the pixel size
of 14 μm, and the EB-CCD sensor 132 has the pixel size of 7 μm, the
EB-CCD sensor 131 is used to adjust the optical axis of the electron
beam, adjust the image, and extract electron image acquisition
conditions. Next, the EB-CCD sensor 131 is moved by the moving mechanism
M to a position away from the optical axis, so that the electron beam is
incident on the fluorescent plate 15. An optical signal converted from
electrons by the fluorescent plate 15 is incident on the TDI sensor 17
through the FOP 16. In this way, the camera 19 captures electron images
in succession using the output of the TDI sensor 17. Thus, it is possible
to perform, for example, an inspection of an LSI wafer for defects, an
inspection of an exposure mask, and the like. Using or referring to
setting conditions for the electro-optical system extracted by the EB-CCD
sensor 131, the image capturing in the TDI detector 12 is performed in
the camera 19. Such image capturing can be performed simultaneously with
an inspection for defects (i.e., on-line) or after the image capturing
(i.e., off-line).

[0161]In an inspection for defects, information such as the location,
type, size and the like of defects can be provided. After the image
capturing and inspection for defects in the TDI detector 12, the moving
mechanism M is actuated to move the EB-CCD sensor 132 to the position of
the optical axis, allowing the EB-CCD sensor 132 to capture images. In
this event, since the location of defects has been known from the
previously acquired result of the inspection for defect through the image
capturing in the TDI detector 12, the EB-CCD sensor 132 performs image
capturing for evaluating the defects in greater detail. In this event, in
addition to a high-resolution image capturing resulting from the smaller
pixel size of the EBG-CCD sensor 132, electron images can be captured
with an increased number of electrons taken for an image, or with a
longer image capturing duration. When the image capturing time is
prolonged to increase the number of electrons acquired per pixel (the
number of electrons per pixel), an electron image of miniature defects
can be more clearly captured with high contract (high MTF condition) to
acquire data. This is because a larger number of electrons per pixel
results in a reduction in noise component due to fluctuations in
luminance and the like to improve the S/N ratio and MTF. In this way, the
EB-CCD sensor 132 having a smaller pixel size can be used to evaluate
defects in detail, for example, the type, size and the like of the
defects in detail. The ability to evaluate the type of defect in detail
can lead to improvements on the process by feeding back information on
where and how many defects of the same type have occurred, and the like,
to the process.

[0162]Fluctuations in luminance are caused by fluctuations in the number
of incident electrons, fluctuations in the amount of electrons to light
conversion, fluctuations in noise level of the sensor, statistic noise,
and the like. Also, when there is an electronic amplifier such as MCP,
the fluctuations in the number of electrons by electron amplification
constitute a factor as well. Such fluctuation noise can be reduced by
increasing the number of electrons, and can be reduced to approximately a
root value of an output luminance value at the highest noise fluctuation
level (for example, the noise fluctuation level is 700 0.5 with 700
halftone values). Showing an example of the number of electrons per pixel
in each detector, the EB-CCD sensor 131 presents 20-1000 per pixel; the
EB-CCD sensor 132 200-200000 per pixel; and the TDI detector 12 10-1000
per pixel.

[0163]When a plurality of detectors are implemented such that they are
switched for use in particular functions as shown in FIG. 6, one and the
same inspecting apparatus can perform both inspection and detailed
evaluation on defects. Conventionally, a wafer is moved to a dedicated
analyzer (review SEM or the like) after an inspection for evaluating the
type and size of defects in detail. When the detailed evaluation can be
performed in the same apparatus, it is possible to make shorter and more
efficient the detail evaluation of the inspection for defects and
improvements in process.

[0164]Even when a single EB-CCD sensor 13 is provided, as has been
described in connection with FIGS. 3 to 5, defects can be evaluated after
inspecting the defects through image capturing using the TDI detector 12,
in which case the number of acquired electrons per pixel is increased to
reduce noise fluctuation components before the defects are evaluated. In
this way, the type and size of the defects can be evaluated without using
a dedicated defect analyzer, and even if it is used, the defect analyzer
can be reduced, and improvements in process and process management can be
more efficiently accomplished.

[0165]In the embodiment so far described, the mechanism for switching the
CCD detector 11 and TDI detector 12 utilizes mechanical movements. In
contrast, FIG. 7 is a diagram schematically showing a fifth embodiment of
an inspecting apparatus according to the present invention, where an
electronic deflector is utilized for a switching mechanism. While this
embodiment also uses a single CCD detector 11 and a single TDI detector
12 by selectively switching them, the CCD detector 11 is placed out of
the optical axis (trajectory of an electron beam e) at a predetermined
angle to the optical axis, as shown. Also, a deflector 41 is disposed on
the optical axis for switching the trajectory of the electron beam e
between the CCD detector 11 and the TDI detector 12. The deflection angle
of the deflector 41 is preferably in the range of 3 to 30°. This
is because excessive deflection of secondary beam would result in
distortions in a two-dimensional image and larger aberration.

[0166]In this embodiment, the EB-CCD sensor 13 is electrically connected
to a camera 44 through a wire 42 and a feed through flange 43. Thus, when
the CCD detector 11 is used, the trajectory of the electron beam e is
deflected by the deflector 41, such that the electron beam e is
perpendicularly incident on the EB-CCD sensor 13. The incident electron
beam e is converted into an electric signal by the EB-CCD sensor 13, and
the electric signal is transmitted to the camera 44 through the wire 42.
On the other hand, when the TDI detector 12 is used, the deflector 41 is
not operated. Consequently, the electron beam e is incident on the
fluorescent plate 15 directly or through the MCP 14. The electron beam
incident on the fluorescent plate 15 is converted into an optical signal
which is transmitted to a TDI sensor 17 through an FOP 16, and is
converted into an electric signal by the TDI sensor 17 for transmission
to a camera 19.

[0167]FIG. 8 is a diagram schematically showing a sixth embodiment of an
inspecting apparatus according to the present invention, where a CCD
detector 11 and a TDI detector 12 each comprise an electron sensor for
receiving an electron beam. Specifically, the CCD detector 11 employs an
EB-CCD sensor 13, whereas the TDI detector 12 employs an EB-TDI (electron
bombardment time delay integration) sensor t1 as an electron sensor,
causing an electron beam e to be directly incident on the EB-TDI sensor
51. In this configuration, the CCD detector 11 is used to adjust the
optical axis of the electron beam, as well as adjust and optimize image
capturing conditions. On the other hand, when the EB-TDI sensor 51 of the
TDI detector 12 is used, the EB-CCD sensor 13 is moved by the moving
mechanism M to a position away from the optical axis, as previously
described, before an image capturing is performed by the TDI detector 12
using or referring to conditions which have been found when the CCD
detector 11 is used, to perform evaluation or measurement.

[0168]As described above, in this embodiment, a semiconductor wafer can be
inspected for defects by the EB-TDI sensor 51 using or referring to
electro-optical conditions which have been found when the CCD detector 11
is used. Also, an evaluation on defects can be performed for the type,
size and the like of the defects using the CCD detector 11 after the
inspection for the defects by the TDI detector 12.

[0169]The EB-TDI sensor 51 is, for example, in a rectangular shape, with
its pixels arranged in a two-dimensional array such that the electron
beam e can be directly received thereby for use in forming an electron
image, where the image size is in the range of 5-20 μm, the number of
pixels is in the range of 1000-8000 in the horizontal direction and
1-8000 in the scanning direction, and the gain is in the range of
10-5000. The EB-TDI sensor 51 can be used at a line rate of 1 kHz to 1
MHz. The gain is dictated by the energy of incident electrons. For
example, when an incident electron beam has energy of 4 kev, the gain can
be set in the range of 200 to 900, and the gain can be adjusted by the
sensor structure with the same energy. In this way, when the EB-TDI
sensor is used in an apparatus for capturing an electron image, the
apparatus can advantageously capture images in succession, as well as
achieve higher MTF (or contrast) and a higher resolution, as compared
with a TDI sensor for sensing light.

[0170]Actually, in this embodiment, the TDI detector 12 is also formed
into the shape of package, so that the package itself serves as a feed
through, with pins 18 of the package connected to the camera 19 on the
atmosphere side. When configured as shown in FIG. 8, it is possible to
eliminate disadvantages such as a loss in optical conversion due to FOP,
optical glass for hermetic sealing, optical lenses and the like,
aberration and distortion during optical transmissions and degradation in
image resolution caused thereby, failed detection, high cost, increase in
size, and the like, as compared with the first to fifth embodiments so
far described.

[0171]FIG. 9 is a plan view showing pixels P11-Pij on a sensor plane 51'
of an EB-TDI sensor 51. In FIG. 9, an arrow T1 indicates an integration
direction of the sensor plane 51', which is a direction perpendicular to
a T2 integration direction T1, i.e., a direction in which a stage S is
moved in succession. The pixels P11-Pij of the sensor t1 are arranged in
500 steps in the integration direction T1 (number of integration steps
i=500), and 4000 (j=4000) in the successive movement direction T2 of the
stage S.

[0172]FIG. 10 is a diagram schematically showing the positional
relationship between the EB-TDI sensor 51 and a secondary electron beam.
In FIG. 10, when a secondary electron beams EB emitted from a wafer W is
emitted from the same positions of the wafer W for a certain time, the
secondary electron beam EB is sequentially incident on a series of
positions a, b, c, d, e, . . . on a projection optical system MO in the
order of a to in association with successive movements of the stage S.
The secondary electron beam EB incident on the projection optical system
MO is sequentially emitted from a series of positions a', b', c', d', e',
. . . , i' on the projection optical system MO. In this event, when a
charge integration movement in the integration direction T1 of the EB-TDI
sensor 51 is synchronized with the successive movements of the stage S,
the secondary electron beams EB emitted from the positions a', b', c',
d', e', . . . , i' on the projection optical system MO are sequentially
incident on the same positions on the sensor plane 51', so that the
charge can be integrated by the number of integration steps i. In this
way, each pixel P11-Pij on the sensor plane 51' can acquire more signals
of radiated electrons, thereby accomplishing a higher S/N ratio, and
capturing a two-dimensional image at high speeds. The projection optical
system MO has a magnification of 300 times, by way of example.

[0173]FIG. 11 is a diagram schematically showing a seventh embodiment of
an inspecting apparatus according to the present invention. As can be
seen from the figure, a TDI detector 12 comprising an electron sensor for
detecting an electron beam is used instead of the TDI detector 12
comprising an optical sensor in the fifth embodiment shown in FIG. 7.

[0174]Likewise, in this embodiment, an EB-CCD sensor 13 of a CCD detector
11 is electrically connected to a camera 44 through a wire 42 and a feed
through flange 43. When the CCD detector 11 is used, the trajectory of
the electron beam is deflected by a deflector 41, such that the electron
beam e is incident perpendicularly to the EB-CCD sensor 13. The incident
electron beam is converted into an electric signal by the EB-CCD sensor
13 for transmission to the camera 44 through the wire 42. On the other
hand, when the TDI detector 12 is used, the deflector is not operated, so
that the electron beam e is directly incident on the EB-TDI sensor 51 for
conversion into an electric signal which is then transmitted to a camera
19.

[0175]FIG. 12 is a diagram schematically showing an eighth embodiment of
an inspecting apparatus according to the present invention, where a CCD
detector 11 and a TDI detector 12 each comprises an optical sensor for
detecting light, and are configured to be switched by making use of
deflection of electron beam. Specifically, the CCD detector 11 comprises
a CCD sensor for detecting light instead of the EB-CCD sensor 13. The CCD
detector 11 comprises an MCP 61 for amplifying an electron beam; a
fluorescent plate 62 for converting an amplified electron beam into
light; an optical lens 63 for converging light exiting the fluorescent
plate 62 and transmitting a light transmission area of a feed through
flange 43; a CCD sensor 64 for converting light converged by the optical
lens into an electric signal; and a camera 44 for capturing an image
using the electric signal.

[0176]In this embodiment, the two detectors, i.e., the TDI detector 12 and
CCD detector 11 are disposed in a single vacuum chamber, but three or
more detectors may be provided as long as the size of the vacuum chamber
permits. Also, as described above, the MCPs 14, 61 may be omitted if the
amplification of electrons is not required.

[0177]A deflector 41 is provided in this embodiment for switching the
trajectory of the electron beam to the TDI detector 12 or to the CCD
detector 11. Thus, when the CCD detector 11 is used, the electron beam e
is deflected by 5 to 30 degrees by the deflector 41 such that electrons
are incident on the fluorescent plate 62 through the MCP 61 or without
the intervention of the MCP 61. After an electro-optical conversion has
been made herein, optical image information is converged by the optical
lens 63 mounted in the feed through flange 43 and directed into the CCD
sensor 64. The optical lens 63 and CCD sensor 64 are placed in the
atmosphere. The optical lens 63 is provided with a lens (not shown) for
adjusting aberration and focus.

[0178]On the other hand, when the TDI detector 12 is used, the deflector
41 is not operated, permitting the electron beam e to travel directly to
be incident on the MCP 14, or on the fluorescent plate 15 when the MCP 14
is not used. An electro-optical conversion is performed by the
fluorescent plate 15, and the optical information is transmitted to the
TDI sensor 17 through the FOP 16.

[0179]In the eighth embodiment shown in FIG. 12, the CCD sensor 64 is
placed on the atmosphere side, while the TDI sensor 17 is placed in a
vacuum. On the other hand, in a ninth embodiment of an inspecting
apparatus according to the present invention, schematically shown in FIG.
13, a TDI sensor 17 and a CCD sensor 64 are placed on the atmosphere
side. In this embodiment, since the configuration of the CCD detector 11
is the same as that shown in FIG. 12, a description thereon is omitted
herein. The TDI detector 12 comprises an MCP 14, a fluorescent plate 15,
an optical lens 17, a TDI sensor 17, and a camera 19. An electron beam e,
which travels straight without being deflected by the deflector 41, is
amplified by the MCP 14, or is directly incident on the fluorescent plate
15, when the MCP 14 is not used, to undergo an electro-optical conversion
thereby, and the optical information is converged by an optical lens 71
mounted in a hermetic flange 72, and is incident on the TDI sensor 17. In
this way, the trajectory of the electron beam e is switched by the
deflector 41 such that the CCD detector 11' and TDI detector 12 can be
selectively used.

[0180]FIG. 14 is a diagram schematically showing a tenth embodiment of an
inspecting apparatus according to the present invention, where a CCD
detector 11 and a TDI detector 12 each comprise an optical sensor for
detecting light. These optical sensors are disposed within a single
chamber, and the detectors are switched through translation or rotation.
Specifically, the CCD sensor 64 of the CCD detector 11 and the TDI sensor
17 of the TDI detector 12 are disposed within a single vacuum chamber MC.
In this embodiment, since the TDI detector 12 is the same as that shown
in FIG. 12, a repeated description is omitted herein. The CCD detector 11
comprises an MCP 61, a fluorescent plate 62, an FOP 81, and a CCD sensor
64. When the TDI detector 12 is used, the CCD detector 11 is moved by a
moving mechanism M to go away from the optical axis of the electron beam
e (to the right in the figure). In either of the detectors, during use,
the electron beam e is amplified by MCP 14, 61, or is directly incident
on the fluorescent plate 15, 62 without using the MCP 14, 61 to undergo
an electro-optical conversion, and the resulting optical information is
transmitted to the sensor 17, 64 through the FOP 16, 81 for conversion
into an electric signal which is then captured by the camera.

[0181]FIG. 15 is a diagram schematically showing an eleventh embodiment of
an inspecting apparatus according to the present invention, where a
moving mechanism is used in combination with a deflector 41 as a
switching mechanism such that one can be selected from five detectors. In
FIG. 15, an EB-CCD sensor 92 of a first detector, an EB-CCD sensor 93 of
a second detector, and an EB-CCD sensor 94 of a third detector are
mounted in a cylindrical shield block 91 which translates in a direction
indicated by an arrow by the moving mechanism M. A shield hole 95 is
formed through the shield block 91 at a proper site for passing an
electron beam e therethrough, and an EB-TDI sensor 51 of a fourth
detector is provided on a trajectory along which the electron beam e
travels straight after it has passed through the shield hole 95. Further,
a TDI detector 12, which is a fifth detector, is provided at a position
at which it receives the electron beam which has been deflected by the
deflector 41 in the trajectory direction and passed through the shield
hole 95. The shield block 91 used herein may be a cylindrical structure
of 1-100 mm diameter, by way of example, which is preferably made of such
a material as a metal such as titanium, phosphor bronze, aluminum or the
like, or a non-magnetic material, or aluminum plated with gold or
titanium plated with gold may also be used.

[0182]Thus, when an image is captured by any of the EB-CCD sensors 92-94
of the first to third detectors, the shield block 91 is moved by the
moving mechanism M without actuating the deflector 41, such that the
center of any EB-TDI sensor may be moved to the position of the
trajectory of the electron beam e. When the electron beam is incident on
the EB-TDI sensor of the fourth detector, the shield block 91 is moved by
the moving mechanism M without actuating the deflector 41 to a position
at which the electron beam can pass through the shield hole 95. Also,
when an image is captured by the TDI detector 12 which is the fifth
detector, the deflector 41 is actuated, and the shield block 91 is moved
by the moving mechanism M to a position at which the electron beam can
pass through the shield hole 95.

[0183]The EB-CCD sensors 92-94, TDI sensor 17, and EB-TDI sensor 51 used
in this embodiment differ from one another in performance such as the
element size, driving frequency, sensor size and the like, depending on
their respective uses and purposes. One example is listed below.

[0196]Describing an exemplary usage of a plurality of sensors as mentioned
above, the EB-CCD sensor 92 is used to adjust the electro-optical system
of the optical beam, i.e., for optimization of lens conditions, aligner
conditions, magnification, and stig conditions. While a lens voltage, an
aligner voltage, a stig voltage and the like are controlled by image
processing, such control and image processing are fully automated suing a
personal computer which incorporates an automatic control function.
Images are captured at high speeds using the EB-CCD sensor 92 which
provides a high frame rate to adjust automatic conditions.

[0197]The EB-CCD sensor 93 operates at a frequently used frame rate of 33
Hz, a speed which can be sufficiently determined by the human's eyes.
Therefore, a work for confirming adjustment, and observation of a sample,
for example, observation, evaluation and the like of an image of defects
after an inspection for defects are performed while viewing the image.
When miniature defects are found during observation so that observation,
evaluation, and classification of defects at higher resolution are
desired, the EB-CCD sensor 94 is used. The EB-CCD sensor 94 has smaller
pixels and accordingly a higher resolution, but requires a longer time
for image capturing due to its lower frame rate. It is therefore
necessary to select a site to be observed for image capturing.

[0198]The TDI detector 12 and EB-TDI sensor are properly used in
accordance with their different scan rates (line rates). Generally,
frequencies corresponding to the scan rate of a TDI sensor are limited in
a frequency range supported by a circuit. Also, it is difficult to design
a driving circuit which satisfies both low frequencies and high
frequencies. As such, the E-TDI sensor 51 is used to inspect at high
speeds and at high frequencies, while the TDI detector 12 is used to
perform an inspection for defects at lower frequencies of 1-100 kHz.
However, any of the TDI detector 12 and the EB-TDI sensor 51 may be used
for high frequencies and low frequencies without any hitch. Nevertheless,
since the electron beam directly enters the sensor, the EB-TDI sensor 51
presents a higher sensor temperature. Also, since the EB-TDI sensor 51
suffers from relatively much thermal noise, it is suited to high
frequencies at which a short time is taken for capturing images.

[0199]In the eleventh embodiment shown in FIG. 15, an arbitrary number of
detectors can be disposed within a single vacuum chamber as required. For
example, one or more EB-CCD sensors can be mounted in the shield block 91
in accordance with its length and necessity, and any of the detector
having the EB-TDI sensor 51 and the TDI detector 12 may be omitted.

[0200]FIG. 16 is a diagram schematically showing a twelfth embodiment of
an inspecting apparatus according to the present invention. In the
embodiments so far described, a plurality of detectors or sensors are
disposed within a single vacuum chamber MC in all the embodiments except
for the eighth and ninth embodiments. In this twelfth embodiment, two
vacuum spaces are defined in a single vacuum chamber MC, such that a
detector is disposed in each of the vacuum spaces. Specifically, an
EB-TDI sensor 51 of a TDI detector 12 is disposed in one space of the
vacuum chamber MC, while an EB-CCD sensor of a CCD detector 11 is
disposed in the other vacuum space coupled to the vacuum chamber MC. For
implementing this, a port 101 is provided so as to extend from the vacuum
chamber MC at a proper position in FIG. 16, and one end thereof is
connected to one end of a vacuum chamber MC', which provides the other
vacuum space, through a gate valve 102. The other end of the vacuum
chamber MC' is sealed by a feed through flange FF'. An EB-CCD sensor 13
is disposed within the vacuum chamber MC' which provides the other vacuum
space, and the EB-CCD sensor 13 is connected to a camera 44 on the
atmosphere side through a wire 42 which passes through the feed through
flange FF'.

[0201]In FIG. 16, when the electron beam is incident on the EB-CCD sensor
13 disposed in the vacuum chamber MC', the traveling direction of the
electron beam e is switched by the deflector 41, and the gate valve 102
is opened. An output signal from the EB-CCD sensor 13 is transmitted to
the camera 44 through the wire 42.

[0202]Advantageously, with the EB-CCD sensor 13 which is disposed in a
different vacuum space from the vacuum space in which the EB-TDI sensor
51 is disposed, the one vacuum space is not open to the atmosphere only
if the gate valve 102 is closed, when the EB-CCD sensor 13 is changed.
However, due to different conditions for focusing on the sensor plane
(distance, magnification and the like), it is necessary to establish
appropriate focusing conditions for the electron beam by controlling a
voltage applied to a lens (not shown) placed in front of the deflector
41.

[0203]As described above, in the first to twelfth embodiments, the EB-CCD
sensor, TDI sensor, EB-TDI sensor, and CCD sensor are disposed within a
vacuum chamber, so that images can be captured with high contrast and
high resolution, and a higher throughput and a lower cost can be
accomplished because of the elimination of optical transmission loss, as
compared with conventional approaches.

[0204]In regard to the number of pixels, arbitrary numbers of pixels may
be selected for the TDI sensor, CCD sensor, EB-TDI sensor, and EB-CCD
sensor used in the first to twelfth embodiments. The numbers of pixels
used in general are shown below:

[0213]The numbers of pixels listed above are merely exemplary, and
intermediate values between the foregoing numbers of pixels, or larger
numbers of pixels can be used as well. While the TDI sensor and EB-TDI
sensor typically integrate (scan) in the vertical direction, they may
have one pixel in the vertical direction (for example, 2000×1) if
there are sufficient input signals. On the other hand, while the TDI
sensor and EB-TDI sensor operate at line rates of 1 kHz to 1 MHz (moving
speed in the integration direction), they are often used at 10 to 500
kHz. While the CCD sensor and EB-CCD sensor operate at frame rate of 1 to
1000 Hz, they are typically used at 1 to 100 Hz. These frequencies are
selected to appropriate values depending on applications such as
adjustments of the electro-optical system, observation of review, and the
like.

[0214]When a sensor having a large pixel size is disposed in the vacuum
chamber MC, a larger number of pins are required such as pins for
transmitting sensor driving signals, control signals and output signals,
common pins, and the like. For example, the number of pins can amount to
approximately 100-500 in some cases. With the number of pins thus
increased, difficulties are experienced in the connection with the feed
through flange using a normal contact socket. Also, the normal contact
socket suffers from a high insertion pressure which will exceeds 100
g/pin. If the insertion pressure exceeds 1 kg/cm2 when a sensor
package is fixed, the package can be damaged. For example, with a
securing member for fixation of approximately 4 cm2, a securing
pressure must be limited to 4 kg/4 cm2 or less. Assuming that there
are 100 pins with a required insertion pressure of 100 g/pin, the
securing pressure amounts to 10 kg, resulting in damages of the package.
It is therefore important to use a connection socket which has a
resilient member such as a spring for connection of the package with pins
of the feed through flange. Such a connection socket incorporating a
resilient member can be used with an insertion pressure of 5-30 g/pin, so
that the package can be fixed without damages, and driving signals and
output signals can be transmitted therethrough without problem. Also,
when a sensor is used in vacuum, the emission of gas is problematic.
Accordingly, a connection socket used therefor may be formed with a vent
hole, the interior and periphery of which is plated with gold.

[0215]Generally, a sensor is placed in a ceramic package, where required
wires are connected to wire pads of the ceramic packages by wire bonding
or the like. The ceramic package has wires incorporated therein, and is
provided with connection pins on the back surface thereof (opposite to
the surface on which the sensor is mounted). The connection pins are
connected to pins of a feed through flange by connection parts. Pins
outside of the feed through flange (on the atmosphere side) are connected
to a camera.

[0216]Now, a description will be made on the moving mechanism M which is
used in the embodiment so far described. FIG. 17 schematically shows the
moving mechanism for translating the EB-CCD sensor 13. The moving
mechanism M comprises a shield block 112 which is a cylindrical or hollow
prism member extending through an opening 111 formed through a vacuum
chamber MC at an appropriate position, and the EB-CCD sensor 13 and a
circuit board 113 are provided in the shield block 112. The shield block
112 is formed with a shield hole 114 having a size similar to that of the
EB-CCD sensor 13 or a size of approximately 0.5 to 1 mm, through which an
electron beam is incident on the EB-CCD sensor 13. The shield hole 114
serves as a noise cut aperture for removing unwanted electrons. The
shield block 112 is provided for preventing electron beams from impinging
on insulated portions to cause charge-up to impede normal operations. In
this regard, a preferable material for the shield block 112 is a metal
such as titanium, phosphor bronze, aluminum or the like, or a
non-magnetic material, in order to reduce the influence of a metal oxide
film and sticking of contamination. Alternatively, aluminum plated with
gold or titanium plated with gold may also be used for the shield block
112.

[0217]On end of the shield block 112 is coupled to a feed through flange
116 fixed to a bellows arranged to surround the periphery of the opening
111. Therefore, wires extending from the circuit board 113 are connected
to a camera 118 through the feed through portion 117 of the feed through
flange 116. The wires 42 are routed to pass through a hollow portion of
the shield block 112, which is considered to prevent electron beams from
impinging on the wires 42. This is because electron beams impinging on
the wires 42 cause charge-up on the wires 42, resulting in adverse
affects such as a change in the trajectory of the electron beams.

[0218]On end of the feed through flange 116 is coupled to a ball screw
mechanism 119, and a rotary motor 120 or a rotary handle is connected to
an end of the ball screw mechanism 119. Further, both ends of the feed
through flange 116 are coupled to a guide rail 121 which extends from the
vacuum chamber MC. As such, as the rotary motor 120 is actuated or the
handle is turned, the ball screw mechanism 119 translates in a direction
perpendicular to the wall surface of the vacuum chamber MC, and the feed
through flange 116, in association therewith, moves along the guide rail
121, causing translations of the shield block 112 as well as the EB-CCD
sensor 13 and circuit board 113 contained therein. As a result, it is
possible to selectively create a scenario in which the electron beam is
incident on the EB-CCD sensor 13, and a scenario in which the EB-CCD
sensor 13 is moved such that the electron beam is incident on the TDI
detector 12.

[0219]Next, FIG. 18 schematically shows the configuration of a moving
mechanism M for causing translations using an air actuator mechanism
instead of the rotary motor. As described in connection with FIG. 17, the
EB-CCD sensor 13 and circuit board 113 are disposed within the shield
block 112 which passes through the opening 111 formed through the vacuum
chamber MC at an appropriate position. The shield block 112 is formed
with the shield hole 114 for causing the electron beam to be incident on
the EB-CCD sensor 13. Also, one end of the shield block 112 is coupled to
the feed through flange 116 fixed to the bellows 115 arranged to surround
the periphery of the opening 111. The wires 42 extending from the circuit
board 113 are connected to the camera 118 through the feed through
portion 117 of the feed through flange 116. Further, a shield hole 114'
is formed through the shield block 112 at an appropriate position for
causing the electron beam to be incident on the TDI detector 12 when the
EB-CCD sensor 13 is moved.

[0220]On the other hand, an opening 131 is also formed through a wall
surface opposite to the opening 111, a hollow cylindrical member 132 is
provided to surround the opening 131, and a flange 134 mounted with an
air actuator mechanism 133 is fixed to one end of the cylindrical member
132. The air actuator mechanism 133 comprises a piston 135 coupled to an
end of the shield block 112. The piston 135, which is vacuum shielded by
an O-ring or omni-seal 136, is made movable relative to the flange 134.
Also, the air actuator mechanism 133 comprises a hole 138 for introducing
or exhausting compressed air into or from an air tight chamber 137 for
moving the piston 135 to the left or right in the figure.

[0221]Thus, the air actuator mechanism 133 is actuated to introduce or
exhaust compressed air into or from the air tight chamber through the
hole 138 to move the piston 135 to the right, and simultaneously, the
shield block 112 is moved in the same direction along the guide rail 121,
causing the shield hole 114' to move to a position at which the electron
beam is incident on the TDI detector 12. Conversely, for causing the
electron beam to be incident on the EB-CCD sensor 13, the piston 135 may
be moved to the left to place the shield hole 114 of the shield block 112
at a position on the optical axis of the electron beam. The air actuator
mechanism 133 can be operated with air pressure of 0.1 to 0.5 MPa. For
example, a pressure difference is generated on the piston 1335 by
switching the introduction and exhaustion direction of the compressed
air, for example, by an electromagnetic valve, to operate the air
actuator mechanism 133. In this way, it is possible to selectively create
a scenario in which the electron beam is incident on the EB-CCD sensor
13, and a scenario in which the EB-CCD sensor 13 is moved such that the
electron beam is incident on the TDI detector 12.

[0222]Further, FIG. 19 shows a moving mechanism which utilizes the
rotation. An opening 111 is formed through the wall of a vacuum chamber
MC at an appropriate position, and a cylindrical member 114 is
protrusively arranged to surround the opening 111. A cylindrical shaft
142 is supported by a bearing 143 so as to be rotatable relative to the
cylindrical member 141, and the cylindrical shaft 142 vacuum seals the
cylinder member 141 with a sealing member 144. An omni-seal is a sealing
member made of Teflon, and is effective for the sealing member 144 which
involves movements such as rotation, translation and the like, because of
its small coefficient of dynamic friction. Also, the use of the bearing
143 can stabilize the rotation of the cylindrical shaft 142, and keep
fluctuations of the axis of rotation small.

[0223]An EB-CCD sensor 13, a circuit board 113, and wires 42 are disposed
in the cylindrical shaft 142. The cylindrical shaft 142 has a
flange-shaped end, and a gear 145 is fitted on the periphery of the
cylindrical shaft 142. A feed through flange 116 is attached to the
flange through an O-ring or ICF vacuum sealing structure 146, and a
camera 118 is connected to the feed through flange 116. In the ICF vacuum
seal structure, a sealing member for ICF is used for vacuum sealing. The
wires 42 within the cylindrical shaft 142 are connected to the camera 118
by way of a plurality of pins of the feed through flange 116 for
connection.

[0224]A gear 147 is provided in correspondence to the gear 145 fitted on
the flange at the end of the cylindrical shaft 142. The gear 147 is
driven by a rotary actuator 148. Thus, as a rotating shaft of the rotary
actuator 148 rotates, the gear 147 rotates, causing the gear 145 to
rotate. A rotating angle of the gear 145 can be adjusted by the rotary
actuator 148, so that the actuator can be used with a desired defined
angle such as 90 degrees, 180 degrees and the like. For example, assuming
that the gear ratio is at 1:1, the rotating angle of the rotary actuator
148 may be 90°. In this way, by rotating the rotary actuator 148
by 90°, the electron beam can be selectively incident on any of
the EB-CCD sensor 13 and TDI detector 12.

[0225]A description has been so far made, centered on the detectors, on
its configuration and mechanisms for selective usage thereof. In the
following, the general configuration of an inspecting apparatus
comprising such a detector will be described, including an
electro-optical system, with reference to FIGS. 20 to 23. In these
figures, a detection unit DU is provided with any of the first to twelfth
embodiments, and an electro-optical system is provided at the preceding
stage to the detection unit DU. The detection unit DU preferably has the
ability to form a two-dimensional image. For this purpose, it is
necessary to employ a detector which receives an electron beam
representative of a two-dimensional electron image to form a
two-dimensional image. As previously described, there are a detector
which employs an EB-CCD sensor and/or an EB-TDI sensor on which electrons
are directly incident, and a detector which detects light converted from
incident electrons using a CCD sensor and/or a TDI sensor.

[0226]First, an inspecting apparatus shown in FIG. 20 is an example which
is combined with a detection unit which includes an electron source, a
projection optical system, and a plurality of detectors. A primary
electron beam emitted from an electron gun 151 passes through a lens 152,
an apertures 153, 154, and a lens 155 in this order, and is incident on
an ExB filter 156. The primary electron beam, which travels in a
direction deflected by the ExB filter 156, passes through a lens 157, an
aperture 158, and lenses 159, 160, and is irradiated to the surface of a
wafer W carried on an XYZθ stage S. The wafer W is, for example, an
Si wafer of 300 mm diameter, which is formed thereon with a pattern
structure in the middle of a semiconductor circuit manufacturing process.
The stage S can move in three orthogonal directions, X-, Y-,
Z-directions, and rotate in a θ-direction, and the wafer W is fixed
on the stage S by an electrostatic chuck.

[0227]Electron beams emitted from the surface of the wafer W represents a
two-dimensional electron image which reflects the shape of patterns
formed in the surface of the wafer. The electron beams emitted from the
wafer W pass through the lenses 160, 159, aperture 158, and lens 157, and
travels straight, without being bent by the ExB filter 156, pass through
a lens 161, an aperture 162, a lens 163, and an aligner 164, and is
introduced into the detection unit DU. The electron beams thus introduced
into the detection unit DU are incident on a detector selected from a
plurality of detectors which have been described in the first to twelfth
embodiments. The apertures 158, 162 perform noise cut operations.

[0228]It should be noted that voltages applied to the respective lenses
are set to meet conditions for focusing the emitted electrons at a
predefined magnification. Also, focus adjustment, distortion adjustment,
aligner adjustment, aperture position adjustment, and ExB condition
adjustment are performed as optical axis adjustments. The lenses 157, 159
are tablet lenses which are dual telecentric and accomplish low
aberration and low distortions. This lens system can provide
magnification of 5-1000 times. Distortions are corrected by a stig (not
shown), and conditions for adjustment have been periodically calculated
using a reference wafer. For adjusting the positions of the aligner and
aperture, previously found values are used for a predefined magnification
to be used, and ExB is adjusted using a voltage of the electron source
151, i.e., a value previously found for the energy of the primary
electron beam.

[0229]When a wafer has a pattern of oxide films and/or nitride films, an
optical correction for distortions alone is not sufficient, so that
evaluation points are sampled from a captured image to evaluate shifts in
position for correcting distortions. For example, the wafer may be
compared with CAD data or review SEM image for evaluation with respect to
the horizontal degree, vertical degree, coordinate position, and the
like. Subsequently, an inspection can be made for defects on a die-to-die
or a cell-to-cell basis or the like. IN the die-to-die inspection for
defect, an inspection area is set within a die, and captured images of
the same inspection areas from other dies are compared to determine the
presence/absence and type of defects.

[0230]It should be noted that electron beams emitted from the wafer W may
be any of secondary electrons, reflected electrons, back scattered
electrons, and Auger electrons. Since these electrons differ in energy
from one another, an electron image can be captured by selecting focusing
conditions with the energy of desired electrons. Voltage conditions for
focusing can be previously calculated through simulations or the like.

[0231]The detection of the image of the wafer W in the detection unit DU
involves first moving the stage S such that a predetermined position of
the wafer W can be detected, and next detecting a viewing field
corresponding to a magnification at that position, for example, an image
of an area of 200×200 μm at a magnification of 300 times. By
repeating this operation at high speeds, a plurality of positions are
detected on the wafer W. Likewise, a comparison of images involves
repetitions of operations for moving the stage S to allow the detection
unit DU to detect a desired area on the wafer W and capturing an image,
and comparing captured data with one another. Through such an inspection
process, it is possible to determine the presence/absence of defects such
as debris, defective conduction, defective pattern, missing pattern and
the like, determine the states of the defects, and classify the defects.

[0240]The irradiated current density is controlled by feeding back the
output of the detection unit DU. When the outputs of the CCD detector and
TDI detector are controlled to fall within 50-80% of their saturation
values, they can be used within a range in which the input/output
relationship of these detectors can maintain the linearity (i.e., a range
in which a shift in linearity is 3% or less), so that images can be
highly accurately evaluated. Particularly, with the performance of
shading processing for subtracting background noise, or the like, the
processing effect is low, and pseudo effects can occur to the contrary in
a region with low linearity. Alternatively, the irradiated current
density can be controlled using an image evaluation value by an image
processing system or the like, instead of the output of the detection
unit DU. The control of the irradiated current density using the
contrast, maximum luminance, minimum luminance, average luminance, and
the like of an image is effective in capturing stable images. It is also
possible to perform stable image comparisons by standardizing the
luminance and contrast of images to be compared, i.e., under the same
conditions.

[0241]FIG. 21 shows an example which is configured to use one of UV light,
UV laser light, and X-ray instead of an electron beam in the inspecting
apparatus described in FIG. 20. Specifically, an UV light source 171 is
provided, for irradiating a wafer W with UV light, by way of example,
instead of the electron gun 151, lenses 152, 155, and apertures 153, 154.
In this way, the UV light is incident on the surface of the wafer W as a
primary beam, and optical electrons emitted from the wafer W are enlarged
by a lens, an aperture or the like of an illustrated electro-optical
system, and directed into a detection unit DU which detects an image of
patterns on the wafer W.

[0242]The UV light from the UV light source 171 is actually transmitted to
the wafer W through a hollow fiber, and is irradiated to a viewing field
region near the center of the wafer W, for example, in a region of 300
μm diameter. In this regard, the X-ray or UV laser light may be used
as a primary beam in a similar manner, where optical electrons emitted
from a wafer W irradiated therewith can be utilized to capture an
electron image of patterns on the wafer W.

[0243]FIG. 22 in turn shows an example which employs in combination a
primary electron beam from an electron gun 151, and UV laser light from a
UV laser source 181 for irradiating the surface of a wafer W with the two
types of beams. In this example, as will be understood from the
descriptions made in connection with FIGS. 20 and 21, the primary
electron beam emitted from the electron gun 151 is deflected by an ExB
filter 156 to travel along the optical axis of an electro-optical system,
and is irradiated to the wafer W. Electron beams emitted from the wafer W
travels straight through the electro-optical system. The UV laser used in
combination with the primary electron beam is also incident on the
surface of the wafer W as a primary beam, and optical electrons emitted
therefrom are enlarged by a lens, an aperture and the like of the
illustrated electro-optical system, and are directed into a detection
unit DU which detects an image of patterns on the wafer W. The UV laser
light used herein may be a four-time wave of YAG or exima laser light
which is introduced to the surface of the wafer W through a hollow fiber.

[0244]In the inspecting apparatus so far described in connection with
FIGS. 20 to 22, the lens 160 operates as a control electrode. When the
wafer W includes a number of oxide films and/or nitride films, the wafer
W irradiated with an electron beam readily results in charge-up on the
oxide film or the like on the surface. This will cause the trajectory of
electron beams emitted from the surface of the wafer W to curve, or a
discharge to occur between the wafer W and an electrode, for example, the
lens 159 or the like. This influence is particularly grave in the
projection optical system shown in FIGS. 20 to 22. This is because
electron beam impinges on a wider region at one time, as compared with a
SEM scheme, due to a rectangular or oval shape of the irradiated electron
beam. In the SEM scheme, since converged electron beams are scanned, the
charge-up is mitigated, resulting in a relatively small amount of
charge-up. However, for the reason set forth above, the projection
optical system is more susceptible to charge-up and largely affected
thereby.

[0245]A discharge occurs between the wafer W and the lens 159 because a
potential on the lens 160 is relatively low and can be freely changed,
whereas the lens 159 is applied with a high voltage in the range of 15 to
30 kV which cannot be varied. In this event, a lens electric field
distribution on the surface of the wafer W is determined by the voltage
applied to the lens 159, and a voltage applied to the wafer W (for
example, -3 kV), for example, 1-3 kV/mm. Therefore, the lens 160 is used
to adjust the electric field distribution on the surface of the wafer W
by adjusting the voltage applied to the lens. By adjusting the voltage of
the lens 160, the electric field distribution on the surface of the wafer
W can be adjusted in the range of 0.1 to 1 kV/mm, thus restraining the
discharge. This is because, by debilitating the positive electric field
distribution, an initial acceleration of electrons emitted from the
surface of the wafer W can be reduced, i.e., an emitted electric field
strength can be debilitated, to reduce the emission of electrons which
contribute to the discharge.

[0246]Actually, it is thought that electrons are more likely to be emitted
at corners and in regions with high electric field strength. For example,
assuming that an insulating film is positively charged up, and a
miniature plug structure electrically conducted to a lower layer exists
below the insulating film, the plug is at a substrate potential (for
example, -3 kV), with the surrounding insulator positively charged up.
When the surface of the plug has a diameter of 100 nm, and the charge-up
is +10 V, the average electric field strength of the plug is calculated
to be 100 kV/mm. Further, if the electric field strength increases in
fine gaps and asperities in a boundary region between the plug and the
insulator beyond 108-109 V/mm, by way of example, electrons
will be emitted, causing a discharge to readily occur.

[0247]Next, FIG. 23 shows an example off a transmission-type inspecting
apparatus. While the inspecting apparatus shown in FIGS. 20 to 22
irradiates a wafer with an electron beam, UV light, or UV laser light to
use electrons emitted from the wafer, the inspecting apparatus shown in
FIG. 23 inspects a sample utilizing electrons which are generated by an
electron beam that has transmitted a sample. Specifically, an electron
beam emitted from an electron gun 151 passes through a lens 191 and an
aperture 192 to control the angle of electrons and the amount of
electrons incident on zoom lenses 193, 194. An incident angle to the
aperture 195 is controlled by these lenses. The electron beam, which has
been adjusted for the amount of electrons by the aperture 195, is made
parallel with the optical axis by a lens 196, and irradiated to a sample
SL. By adjusting voltages applied to the zoom lenses 193, 194, the
zooming magnification is change, for example, from one to 200 times, and
the size of the electron beam irradiated to the sample SL is controlled
to have the diameter, for example, in the range of 5 to 1000 μm.

[0248]The electron beam which has passed through or transmitted the sample
SL is enlarged by a secondary optical system which comprises lenses 197,
198, 200, 201, 203, and apertures 199, 202, and is introduced into a
detection unit DU. The lens 197 comprises an electrode for adjusting the
electric field strength with the sample SL. The lenses 198, 200 are
doublet lenses and satisfy dual centric conditions, and therefore provide
electron images with low aberration. The lenses 201, 203 are lenses for
enlarging an electron image. The lens 203 is adjusted such that the
electron beam is focused on the sensor of the detection unit DU, the
fluorescent plate, or the surface of the MCP. The apertures 199, 202
control aberration and the amount of electrons introduced into the
detection unit DU.

[0249]The sample SL can be any arbitrary item such as an exposure mask, a
stencil mask, a micro-machine having a miniature structure, MEMS parts
and the like, in addition to a semiconductor wafer and a semiconductor
device. It is necessary to adjust the energy of the electron beam
irradiated to the sample in accordance with the characteristics of each
sample, such as the material, pattern shape, and the like of the sample
SL. For permitting the electron beam to transmit the sample SL, high
energy is required, and can be 50-100 keV in some cases. With a sample SL
having openings such as holes, slits and the like, and/or interstices,
for capturing electron beams which have passed through such openings and
interstices, the electron gun 151 is required to generate electrons of
10-10000 eV. For example, assume that a sample SL is irradiated with an
electron beam having energy of 5 keV, generated from the electron gun
151. In this event, assuming that the potential of the sample is -4 kV,
the electron beam is incident on the sample SL at 1 kev. The electron
beam which has passed through the sample SL reflects patterns on the
sample SL, and is introduced into the detection unit DU.

[0250]In the inspecting apparatus which has been described above with
reference to a variety of embodiments, the CCD sensor or EB-CCD sensor is
used to capture a still image, and adjustment of beam axis, observation
of sample, inspection for defects, capturing of review image, review
observation, measurement, and evaluation can be performed utilizing a
step-and-repeat function. In the following, the step-and-repeat function
will be described with reference to FIG. 24. FIG. 24(A) schematically
shows the positional relationship between a wafer W and a plurality of
dies 211. As shown, a notch 212 is formed in a right-hand region. The
dies 211 include a plurality of patterns, classified into a cell pattern
area and a random pattern area, and therefore, a plurality of types of
cells and random pattern areas exist. The size of the dies is generally
on the order of 1×1 mm to 30×30 mm, though it depends on a
wafer of a process.

[0251]As shown in FIGS. 23(B) and 23(C), a care pattern 213 refers to a
pattern portion for which an inspection, a measurement, or an evaluation
is desired, within such a pattern, and a particular site 214 refers to a
portion which should be particularly noted. The particular sites include,
for example, a site which is highly likely to become defective during a
process period due to difficulties in processing because of a small
pattern size, a defective site after an inspection for defects, a site
which is evaluated for a shift in position with an underlying lager in a
lamination process, a turn site for evaluating distortion and aberration
of the electro-optical system, and the like. For the particular sites as
listed above, the step-and-repeat is performed using a CCD sensor or an
EB-CCD sensor to compare required images, evaluate shifts, to observe
details, and so on.

[0252]For inspecting a care area in a cell portion for defects, patterns
are compared with one other in repeated pattern areas in the cell
portion. For example, a viewing field of 5×5 to 500×500 μm
on a sample surface can be observed in a capturing time of 10 to 100
minutes with a magnification of approximately 50 to 1000. As one still
image (CCD image or EB-CCD image) has been captured, the observation area
is moved by a predefined distance to capture the same pattern in a
similar manner. With repeated patterns, the next one of successive
patterns is captured. In this way, a plurality, generally, three or more,
of the same patterns are captured, and the captured images are compared
with one another. As the result of the comparison, if there is only one
different pattern or contrast, or the like, this part is regarded as
defective. Such an inspection is made simultaneously with the image
capturing (on-line), or after capturing inspected images (off-line), to
classify the coordinates and types of defective sites.

[0253]For inspecting random patterns for defects, random patterns in care
areas of each die are compared with one another. In this event, a care
area of a random pattern is captured on one die. This may be performed
using any of an approach for capturing a plurality of still images at one
time and an approach for capturing one by one. Next, the inspecting
apparatus is moved to a random pattern in a care area of another die for
capturing. By thus capturing three or more still images, comparing
corresponding patterns with one another, and finding an failure which
exists only on one image, defective patterns, debris, defective contrast,
and the like are sensed. With this inspection, the coordinates of defects
and the type of defects can be classified on-line or off-line. This is
referred to as a die-to-die inspection based on step-and-repeat.

[0254]Otherwise, the inspecting apparatus may be used to evaluate a
positional shift with an underlying layer in a process. In this event,
alignment marks are placed on an underlying layer and an overlying layer
laminated thereon. A positional shift is evaluated by measuring a degree
to which these alignment marks overlap, for example, a shift of the
position of center of gravity, a shift of the centers of representative
lengths from one another, and the like. This evaluation is made after CMP
in a wiring structure for the underlying layer, and after the formation
of resist, or after resist covering and exposure for the overlying layer.

[0255]Examples of alignment marks are shown in FIG. 25. (A) shows a
cross-shaped alignment mark, arranged on an overlying layer and an
underlying layer, which comprises two rectangle of 15 μm long placed
one on the other to appear as a cross shape. Based on how these alignment
marks overlap, the amount of shift is found for a representative position
such as a pattern center position or the like, calculated from the
positions of the centers of gravity of the underlying layer and overlying
layer, and the vertical and horizontal lengths to compare the overlying
and underlying layers. (B) shows a square alignment mark 222 having a
side of 20 μm attached to an underlying layer, and a square alignment
mark 223 having a side of 7 μm attached to an overlying layer, which
overlap one on the other. Likewise, in this event, a positional shift is
evaluated by calculating the center position of the mark from a sift of
the positions of the centers of gravity, and a die row length. In this
regard, the size of the alignment marks is not limited to the values
shown in FIG. 25, but an alignment mark of a smaller size may be used,
for example, a total size of 1×1 μm.

[0256]10-50 of such alignment marks are attached to one wafer. A shift
amount is calculated for each alignment mark, and if there is a relative
directivity in the shift amount (for example, when a larger shift is
found generally in the left-hand direction), the exposure position is
adjusted to make a correction therefor. In this way, with the use of the
step-and-repeat function, the CCD sensor or EB-CCD sensor provides a
higher resolution and MTF, as compared with the TDI detector. When images
can be captured in a situation in which a large number of electrons can
be captured per pixel, inspection for defects, review inspection,
position shift inspection can be performed with high accuracy, taking
advantage of the characteristics of the CCD sensor and EB-CCD sensor.

[0257]As described above, the inspecting apparatus according to the
present invention can use the CCD detector 11 and TDI detector 12 by
switching one to the other, and therefore provides advantages as
described below.

[0258]First, the CCD detector 11 using the CCD sensor or EB-CCD sensor can
be used to capture a still image, while the TDI detector 12 using the TDI
sensor or EB-TDI sensor can be used to capture sequential images by
capturing images while moving the stage device. For switching these
detectors to selectively capturing a still image and sequential images,
the axes of the sensors used in the respective detectors must be in
alignment. It is also necessary that the lens conditions (intensities of
the lenses, beam deflection conditions, and the like) are the same when
the CCD detector 11 is used and when the TDI detector 12 is used.
Further, the primary optical system and secondary optical system must
operate under the same conditions. In this regard, the sensors of the
respective detectors can be corrected for a relative positional shift of
their axes by comparing images captured by the sensor of the CCD detector
11 and the sensor of the TDI detector 12.

[0259]Describing the operation in the inspecting apparatus according to
the present invention in a specific manner, first at step S1, the CCD
detector 11 is placed in front of the TDI detector 12 to capture a still
image to align the primary optical system to the secondary optical
system. Next, after the secondary optical system is adjusted (for
example, the size, magnification, and contrast of secondary beams,
centering of lenses), the size and current density distribution of the
primary beam are adjusted. Subsequently, at step S2, the CCD detector 11
is moved to direct secondary electron beams into the TDI detector 12,
thereby capturing sequential images to ensure sample inspection images.
Further subsequently, at step S3, the CCD detector 11 is removed and
placed in front of the TDI detector 12 to capture a review image which is
then compared with the inspection images captured by the TDI detector 12
to determine whether a defective site confirmed in an inspection image
captured by the TDI detector 12 is a false defect or a true defect.

[0260]It should be noted that in general, the aforementioned step S1 is
performed only for the first one of a plurality of wafers accommodated in
a cassette, while steps S2 and S3 are performed for the second wafer
onward. However, for confirming the stability of the inspection, step S1
may be performed on a periodic basis.

[0261]As described above, since still images can be captured by the CCD
detector 11, the optical system can be adjusted by attaching a standard
chip at an arbitrary end of the stage device, without the need for
transferring a wafer. In other words, a still image of the standard chip
can be captured while a wafer is being loaded, to confirm the
reproductivity of the primary beam, secondary beam, and electron beam
(free of variations). When a difference is found by confirming a
difference between the image of the standard chip and the image of the
wafer, no inspection is performed on the assumption that chucking
conditions of the electrostatic chuck have varied. It is also possible to
check variations in the current density of the primary beam and the beam
size.

[0262]The size, position, and profile of the primary beam are adjusted
with reference to the image captured by the CCD detector 11 at the
aforementioned step S1. Also, when variations in these parameters exceed
a certain basis, the electron gun or FA (aperture plate) is replaced. In
a process of aligning the primary beam to the secondary beam, an image of
low magnification, for example, 30 times, 80 times or the like is used.
However, since the secondary beam locally impinges on MCP when a
low-magnification image is captured, the MCP is locally damaged,
resulting in a failure in detecting defects. Accordingly, the MCP must be
replaced when an observation time at low magnifications has exceeded a
certain time (for example, 1000 hours). On the other hand, the EB-CCD
sensor can be used for a long term because it is not particularly damaged
by the irradiation of the electron beam.

[0263]Also, the secondary beam is aligned with reference to the image
captured by the CCD detector 11. For example, the centering of the
lenses, optimization for operating conditions of the beam deflector (for
example, the ExB separator 3 in FIG. 2) (for example, adjustments to
conditions for projecting an image onto the center of the sensor) can be
performed. In this way, highly accurate adjustments can be accomplished.
For example, the MTF can be adjusted in the range of 30 to 50%. Also, by
using the image captured by the CCD detector 11, it is possible to check
fluctuations in the secondary beam, changes in stig condition, a shift of
the center of lens, fluctuations in beam deflection conditions, and the
like.

[0264]In regard to the image processing system (for example, the image
processing unit 9 in FIG. 2), a step-and-repeat based inspection can be
performed because a still image can be captured by the CCD detector 11.
Also, since the detectors can be rapidly switched, an inspection can be
performed after switching from the TDI detector 12 to the CCD detector 11
when the inspection involves a small number of points under inspection,
such as an overlay inspection. Preferably, the TDI detector 12 is used
for an inspection when the inspection speed is 10 MPPS (mega-pixel/sec)
or higher, and the CCD detector 11 is used for an inspection when the
inspection speed is 10 MPPS or lower. Also, since the sensor of the CCD
detector 11 has been brought into alignment to the sensor of the TDI
detector 12, the sensor of the CCD detector 11 need not be again aligned
when a review image is captured at the aforementioned step S3.

[0265]By incorporating the inspecting apparatus according to the present
invention into a factory network, operation situations such as axis
adjustment, inspection, review and the like can be communicated to a
manager through the factory network, thus permitting the manager to
immediately know failures in apparatuses and defective adjustments and
take appropriate actions therefor.

[0266]Now, an example of a semiconductor manufacturing method performed
using the inspecting apparatus described above will be described with
reference to flow diagrams of FIGS. 26 and 27. As shown in FIG. 26, the
semiconductor device manufacturing method includes, as main processes, a
wafer manufacturing process 231 for manufacturing wafers or a wafer
preparing process for preparing wafers, a mask manufacturing process f236
or manufacturing masks and reticles for use in exposure or a mask
preparing process for preparing masks, a wafer processing process 232 for
performing processing required to the wafer, a chip assembling process
233 for cutting, one by one, chips formed on the wafer and making them
operable, a chip inspecting process for inspecting chips manufactured in
the chip assembling process, and a process for producing products
(semiconductor devices) from chips which have passed the inspection. In
this regard, since the wafer manufacturing process 231, wafer processing
process 232, and lithography process 2323 are known, a description
thereon is omitted here. These main processes are further comprised of
several sub-processes, respectively.

[0267]A main process which exerts critical affections to the performance
of resulting semiconductor devices is the wafer processing process. This
process involves sequentially laminating designed circuit patterns on the
wafer to form a large number of chips which operate as memories or MPUs.
The wafer fabricating process includes sub-processes as shown in an area
surrounded by dotted lines in the figure. Specifically, the wafer
processing process 232 includes a thin film forming sub-process 2321 for
forming dielectric thin films serving as insulating layers, metal thin
films for forming wires or electrodes, and so on using CVD, sputtering
and so on; an oxidation sub-process 2322 for oxidizing metal thin film
layers and wafer substrate; a lithography sub-process 2323 for forming a
resist pattern using masks or reticles for selectively fabricating the
thin film layers and the wafer substrate; an etching sub-process 2324 for
fabricating the thin film layers and the substrate in conformity to the
resist pattern using, for example, dry etching techniques; an
ion/impurity implantation/diffusion sub-process 2325; a resist striping
sub-process; and an inspection sub-process 2326 for inspecting the
fabricated wafer. As appreciated, the wafer processing process 232 is
repeated a number of times equal to the number of required layers to
manufacture semiconductor devices which operate as designed. By applying
the inspecting apparatus according to the present invention to the
inspection sub-process 2326, it is possible to inspect even a
semiconductor device which has miniature patterns. Since a total
inspection can be accomplished, it is possible to manufacture
semiconductor devices which operate as designed to improve the yield rate
of products and prevent defective products from being shipped.

[0268]FIG. 27 shows steps performed in the lithography sub-process 2323 in
FIG. 26. The lithography sub-process 2323 includes a resist coating step
241 for coating a resist on the wafer on which circuit patterns have been
formed in the previous process; a resist exposing step 242 for exposing
the resist; a developing step 243 for developing the exposed resist to
produce a resist pattern; and an annealing step 244 for stabilizing the
developed resist pattern.

[0269]While the inspecting apparatuses according to the present invention
have been described in connection with a variety of embodiments thereof
with reference to the drawings, the present invention is not limited to
such embodiments. For example, in the embodiments so far described, the
sensors and electro-optical systems are disposed within the vacuum
chamber, but the vacuum chamber is not necessarily used in an environment
in which sensors such as the CCD sensor, TDI sensor and the like can
operate.

[0270]Also, while the embodiments shown in FIGS. 3 to 7, FIG. 12, FIG. 14,
FIG. 15, and FIGS. 17 to 19 uses the FOP at one stage, the FOP is not
limited to one stage, but the FOPs can also be used at a plurality of
stages. For example, it is possible to use two FOPs which comprise an FOP
coated with a fluorescent agent for use in combination with MCP, and an
FOP adhered to a TDI sensor and in close contact with the former FOP. In
doing so, the assembly is improved in accuracy and efficiency.
Specifically, if a FOP coated with a fluorescent agent is adhered to a
TDI sensor, contamination and adhesive, if sticking to the fluorescent
agent of the FOP, would be difficult to wash away. Also, when a
fluorescent agent is coated after adhesion, a special process and
technique will be required such that the fluorescent agent is not coated
on the TDI sensor itself. Further, a high level of stringency is required
for an assembling accuracy for the parallelism of the FOP coated with the
fluorescent agent with an MCP and the like, so as not to affect the
resolution and anti-discharge performance. Such intricacy is eliminated
by the use of the aforementioned FOPs at two stages. This is true when a
plurality of FOPs are used.

INDUSTRIAL AVAILABILITY

[0271]As will be understood from the foregoing description, the present
invention relies on a moving mechanism or a deflecting means to select a
detector which provides appropriate performance without requiring a work
for changing one detector to another as before, thus making it possible
to reduce a long time taken for the restoration of a vacuum state after
the exposure to the atmosphere due to the change of the detector, and to
efficiently perform works such as adjustments to certain electro-optical
systems, sequential inspections, defect evaluation, and the like. Also,
the present invention has a great significance in a technological and
industrial sense such as the accomplishment of remarkable improvements on
work efficiency, reduction in cost, higher performance of surface
inspection, higher throughput, and the like.